Neprilysin inhibitors

ABSTRACT

In one aspect, the invention relates to compounds having the formula: 
     
       
         
         
             
             
         
       
     
     where R 1 -R 6 , a, b, Z, and X are as defined in the specification, or a pharmaceutically acceptable salt thereof. These compounds have neprilysin inhibition activity. In another aspect, the invention relates to pharmaceutical compositions comprising such compounds; methods of using such compounds; and processes and intermediates for preparing such compounds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/443,827, filed on Feb. 17, 2011; the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel compounds having neprilysin-inhibition activity. The invention also relates to pharmaceutical compositions comprising such compounds, processes and intermediates for preparing such compounds and methods of using such compounds to treat diseases such as hypertension, heart failure, pulmonary hypertension, and renal disease.

2. State of the Art

Neprilysin (neutral endopeptidase, EC 3.4.24.11) (NEP), is an endothelial membrane bound Zn²⁺ metallopeptidase found in many organs and tissues, including the brain, kidneys, lungs, gastrointestinal tract, heart, and the peripheral vasculature. NEP degrades and inactivates a number of endogenous peptides, such as enkephalins, circulating bradykinin, angiotensin peptides, and natriuretic peptides, the latter of which have several effects including, for example, vasodilation and natriuresis/diuresis, as well as inhibition of cardiac hypertrophy and ventricular fibrosis. Thus, NEP plays an important role in blood pressure homeostasis and cardiovascular health.

NEP inhibitors, such as thiorphan, candoxatril, and candoxatrilat, have been studied as potential therapeutics. Compounds that inhibit both NEP and angiotensin-I converting enzyme (ACE) are also known, and include omapatrilat, gempatrilat, and sampatrilat. Referred to as vasopeptidase inhibitors, this latter class of compounds is described in Robl et al. (1999) Exp. Opin. Ther. Patents 9(12): 1665-1677.

SUMMARY OF THE INVENTION

The present invention provides novel compounds that have been found to possess neprilysin (NEP) enzyme inhibition activity. Accordingly, compounds of the invention are expected to be useful and advantageous as therapeutic agents for treating conditions such as hypertension and heart failure.

One aspect of the invention relates to a compound of formula I:

where:

R¹ is selected from —OR⁷ and —NR⁸R⁹;

R^(2a) is selected from —CH₂OH, —CH₂OP(O)(OH)₂, and —CH₂OC(O)CH(R³⁷)NH₂; or R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹— or is taken together with R⁸ to form —CH₂OO—C(O)—;

R^(2b) is selected from H and —CH₃, or is taken together with R^(2a) to form —CH₂—O—CH₂;

Z is selected from —CH— and —N—;

X is a —C₁₋₉heteroaryl;

R³ is absent or is selected from H; halo; —C₀₋₅alkylene-OH; —NH₂; —C₁₋₆alkyl; —CF₃; —C₃₋₇cycloalkyl; —C₀₋₂alkylene-O—C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; —NHC(O)R²⁴; ═O; —NO₂; —C(CH₃)═N(OH); phenyl optionally substituted with one or two groups independently selected from halo, —OH, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl; naphthalenyl; pyridinyl; pyrazinyl; pyrazolyl optionally substituted with methyl; thiophenyl optionally substituted with methyl or halo; furanyl; and —CH₂-morpholinyl; and R³, when present, is attached to a carbon atom;

R⁴ is absent or is selected from H; —OH; —C₁₋₆alkyl; —C₁₋₂alkylene-COOR³⁵; —CH₂OC(O)CH(R³)NH₂; —OCH₂OC(O)CH(R³⁶)NH₂; —OCH₂OC(O)CH₃; —CH₂OP(O)(OH)₂; —CH₂CH(OH)CH₂OH; —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl; pyridinyl; and phenyl or benzyl optionally substituted with one or more groups selected from halo, —COOR³⁵, —OCH₃, —OCF₃, and —SCF₃; and R⁴, when present, is attached to a carbon or nitrogen atom;

or R³ and R⁴ are taken together to form -phenylene-O—(CH₂)₁₋₃— or -phenylene-O—CH₂—CHOH—CH₂—;

a is 0 or 1; R⁵ is selected from halo, —CH₃, —CF₃, and —CN;

b is 0 or an integer from 1 to 3; each R⁶ is independently selected from halo, —OH, CH₃, —OCH₃, and —CF₃;

R⁷ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₄alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl;

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹²R¹³, —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R¹² and R¹³ are independently selected from H, —C₁₋₆alkyl, and benzyl, or R¹² and R¹³ are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³¹ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —C₁₋₆alkyl or —C_(0.6)alkylene-C₆₋₁₀aryl;

R⁸ is selected from H, —OH, —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, -pyridyl, and —OC(S)NR¹⁵R¹⁶; R¹⁴ is selected from H, —C₁₋₆alkyl, —C₆₋₁₀aryl, —OCH₂—C₆₋₁₀aryl, —CH₂O—C₆₋₁₀aryl, and —NR¹⁵R¹⁶; and R¹⁵ and R¹⁶ are independently selected from H and —C₁₋₄alkyl;

R⁹ is selected from H, —C₁₋₄alkyl, and —C(O)—R¹⁷; and R¹⁷ is selected from H, —C₁₋₆alkyl, —C₃₋₇cycloalkyl, —C₆₋₁₀aryl, and —C₁₋₉heteroaryl;

R¹⁸ and R¹⁹ are independently selected from H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or

R¹⁸ and R¹⁹ are taken together to form ═O;

R²⁰ is selected from H and —C₁₋₄alkyl;

R²¹ and R³⁵ are independently selected from H, —C₁₋₆alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₄alkylene-OC(O)R²⁵, —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R²⁵ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR²⁷R²⁸, —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; R²⁷ and R²⁸ are independently selected from H, —C₁₋₆alkyl, and benzyl; or R²⁷ and R²⁸ are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR²⁷R²⁸; and R³⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl;

R²² and R²³ are independently selected from H, —C₁₋₆alkyl, —CH₂COOH, —(CH₂)₂OH; —(CH₂)₂OCH₃, —(CH₂)₂SO₂NH₂, —(CH₂)₂N(CH₃)₂, —C₀₋₁alkylene-C₃₋₇cycloalkyl, and —(CH₂)₂-imidazolyl; or R²² and R²³ are taken together to form a saturated or partially unsaturated —C₃₋₅heterocycle optionally substituted with halo, —OH, —COOH, or —CONH₂; and optionally containing an oxygen atom in the ring;

R²⁴ is selected from —C₁₋₆alkyl; —C₀₋₁alkylene-O—C₁₋₆alkyl; phenyl optionally substituted with halo or —OCH₃; and —C₁₋₉heteroaryl;

R³⁶ is selected from H, —CH(CH₃)₂, phenyl, and benzyl; and

R³⁷ is selected from H, —CH(CH₃)₂, phenyl, and benzyl;

where each alkyl group in R¹, R³, and R⁴ is optionally substituted with 1 to 8 fluoro atoms; and;

where the methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl;

or a pharmaceutically acceptable salt thereof.

Another aspect of the invention relates to pharmaceutical compositions comprising a pharmaceutically acceptable carrier and a compound of the invention. Such compositions may optionally contain other therapeutic agents. Accordingly, in yet another aspect of the invention, a pharmaceutical composition comprises a compound of the invention as the first therapeutic agent, one or more secondary therapeutic agent, and a pharmaceutically acceptable carrier. Another aspect of the invention relates to a combination of active agents, comprising a compound of the invention and a second therapeutic agent. The compound of the invention can be formulated together or separately from the additional agent(s). When formulated separately, a pharmaceutically acceptable carrier may be included with the additional agent(s). Thus, yet another aspect of the invention relates to a combination of pharmaceutical compositions, the combination comprising: a first pharmaceutical composition comprising a compound of the invention and a first pharmaceutically acceptable carrier; and a second pharmaceutical composition comprising a second therapeutic agent and a second pharmaceutically acceptable carrier. In another aspect, the invention relates to a kit containing such pharmaceutical compositions, for example where the first and second pharmaceutical compositions are separate pharmaceutical compositions.

Compounds of the invention possess NEP enzyme inhibition activity, and are therefore expected to be useful as therapeutic agents for treating patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme or by increasing the levels of its peptide substrates. Thus, one aspect of the invention relates to a method of treating patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme, comprising administering to a patient a therapeutically effective amount of a compound of the invention. Another aspect of the invention relates to a method of treating hypertension, heart failure, or renal disease, comprising administering to a patient a therapeutically effective amount of a compound of the invention. Still another aspect of the invention relates to a method for inhibiting a NEP enzyme in a mammal comprising administering to the mammal, a NEP enzyme-inhibiting amount of a compound of the invention.

Since compounds of the invention possess NEP inhibition activity, they are also useful as research tools. Accordingly, one aspect of the invention relates to a method of using a compound of the invention as a research tool, the method comprising conducting a biological assay using a compound of the invention. Compounds of the invention can also be used to evaluate new chemical compounds. Thus another aspect of the invention relates to a method of evaluating a test compound in a biological assay, comprising: (a) conducting a biological assay with a test compound to provide a first assay value; (b) conducting the biological assay with a compound of the invention to provide a second assay value; wherein step (a) is conducted either before, after or concurrently with step (b); and (c) comparing the first assay value from step (a) with the second assay value from step (b). Exemplary biological assays include a NEP enzyme inhibition assay. Still another aspect of the invention relates to a method of studying a biological system or sample comprising a NEP enzyme, the method comprising: (a) contacting the biological system or sample with a compound of the invention; and (b) determining the effects caused by the compound on the biological system or sample.

Yet another aspect of the invention relates to processes and intermediates useful for preparing compounds of the invention. Accordingly, another aspect of the invention relates to a process of preparing compounds of formula I, comprising the step of coupling a compound of formula 1 with a compound of formula 2:

to produce a compound of formula I; where P¹ is H or an amino-protecting group selected from t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; and where the process further comprises deprotecting the compound of formula 1 when P¹ is an amino protecting group; and where R¹-R⁶, a, b, Z, and X are as defined for formula I. Another aspect of the invention relates to a process of preparing a pharmaceutically acceptable salt of a compound of formula I, comprising contacting a compound of formula I in free acid or base form with a pharmaceutically acceptable base or acid. In other aspects, the invention relates to products prepared by any of the processes described herein, as well as novel intermediates used in such process. In one aspect of the invention novel intermediates have formula 1, 9, 10, 11, 12, or a salt thereof, as defined herein.

Yet another aspect of the invention relates to the use of a compound of formula I or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament, especially for the manufacture of a medicament useful for treating hypertension, heart failure, or renal disease. Another aspect of the invention relates to use of a compound of the invention for inhibiting a NEP enzyme in a mammal. Still another aspect of the invention relates to the use of a compound of the invention as a research tool. Other aspects and embodiments of the invention are disclosed herein.

DETAILED DESCRIPTION OF THE INVENTION Definitions

When describing the compounds, compositions, methods and processes of the invention, the following terms have the following meanings unless otherwise indicated. Additionally, as used herein, the singular forms “a,” “an,” and “the” include the corresponding plural forms unless the context of use clearly dictates otherwise. The terms “comprising”, “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. All numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used herein are to be understood as being modified in all instances by the term “about,” unless otherwise indicated. Accordingly, the numbers set forth herein are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each number should at least be construed in light of the reported significant digits and by applying ordinary rounding techniques.

The term “alkyl” means a monovalent saturated hydrocarbon group which may be linear or branched. Unless otherwise defined, such alkyl groups typically contain from 1 to 10 carbon atoms and include, for example, —C₁₋₄alkyl, —C₁₋₅alkyl, —C₂₋₅alkyl, —C₁₋₆alkyl, —C₁₋₈alkyl, and —C₁₋₁₀alkyl. Representative alkyl groups include, by way of example, methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl and the like.

When a specific number of carbon atoms is intended for a particular term used herein, the number of carbon atoms is shown preceding the term as subscript. For example, the term “—C₁₋₆alkyl” means an alkyl group having from 1 to 6 carbon atoms, and the term “—C₃₋₇cycloalkyl” means a cycloalkyl group having from 3 to 7 carbon atoms, respectively, where the carbon atoms are in any acceptable configuration.

The term “alkylene” means a divalent saturated hydrocarbon group that may be linear or branched. Unless otherwise defined, such alkylene groups typically contain from 0 to 10 carbon atoms and include, for example, —C₀₋₁alkylene-, —C₀₋₆alkylene-, —C₁₋₃alkylene-, and —C₁₋₆alkylene-. Representative alkylene groups include, by way of example, methylene, ethane-1,2-diyl (“ethylene”), propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl and the like. It is understood that when the alkylene term include zero carbons such as —C₀₋₁alkylene-, such terms are intended to include the absence of carbon atoms, that is, the alkylene group is not present except for a covalent bond attaching the groups separated by the alkylene term.

The term “aryl” means a monovalent aromatic hydrocarbon having a single ring (i.e., phenyl) or one or more fused rings. Fused ring systems include those that are fully unsaturated (e.g., naphthalene) as well as those that are partially unsaturated (e.g., 1,2,3,4-tetrahydronaphthalene). Unless otherwise defined, such aryl groups typically contain from 6 to 10 carbon ring atoms and include, for example, —C₆₋₁₀aryl. Representative aryl groups include, by way of example, phenyl and naphthalene-1-yl, naphthalene-2-yl, and the like.

The term “cycloalkyl” means a monovalent saturated carbocyclic hydrocarbon group. Unless otherwise defined, such cycloalkyl groups typically contain from 3 to 10 carbon atoms and include, for example, —C₃₋₅cycloalkyl, —C₃₋₆cycloalkyl and —C₃₋₇cycloalkyl. Representative cycloalkyl groups include, by way of example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.

The term “halo” means fluoro, chloro, bromo and iodo.

The term “heterocycle” is intended to include monovalent unsaturated (aromatic) heterocycles having a single ring or two fused rings as well as monovalent saturated and partially unsaturated groups having a single ring or multiple condensed rings. The heterocycle ring can contain from 3 to 15 total ring atoms, of which 1 to 14 are ring carbon atoms, and 1 to 4 are ring heteroatoms selected from nitrogen, oxygen or sulfur. Typically, however, the heterocycle ring contains from 3 to 10 total ring atoms, of which 1 to 9 are ring carbon atoms, and 1 to 4 are ring heteroatoms. The point of attachment is at any available carbon or nitrogen ring atom. Exemplary heterocycles include, for example, —C₁₋₇heterocycle, —C₃₋₅heterocycle, —C₂₋₆heterocycle, —C₃₋₁₂heterocycle, —C₅₋₉heterocycle, —C₁₋₉heterocycle, —C₁₋₁₁heterocycle, and —C₁₋₁₄heterocyle.

Monovalent unsaturated heterocycles are also commonly referred to as “heteroaryl” groups. Unless otherwise defined, heteroaryl groups typically contain from 5 to 10 total ring atoms, of which 1 to 9 are ring carbon atoms, and 1 to 4 are ring heteroatoms, and include, for example, —C₁₋₉heteroaryl and —C₅₋₉heteroaryl. Representative heteroaryl groups include, by way of example, pyrrole (e.g., 3-pyrrolyl and 2H-pyrrol-3-yl), imidazole (e.g., 2-imidazolyl), furan (e.g., 2-furyl and 3-furyl), thiophene (e.g., 2-thienyl), triazole (e.g., 1,2,3-triazolyl and 1,2,4-triazolyl), pyrazole (e.g., 1H-pyrazol-3-yl), oxazole (e.g., 2-oxazolyl), isoxazole (e.g., 3-isoxazolyl), thiazole (e.g., 2-thiazolyl and 4-thiazolyl), and isothiazole (e.g., 3-isothiazolyl), pyridine (e.g., 2-pyridyl, 3-pyridyl, and 4-pyridyl), pyridylimidazole, pyridyltriazole, pyrazine, pyridazine (e.g., 3-pyridazinyl), pyrimidine (e.g., 2-pyrimidinyl), tetrazole, triazine (e.g., 1,3,5-triazinyl), indolyle (e.g., 1H-indol-2-yl, 1H-indol-4-yl and 1H-indol-5-yl), benzofuran (e.g., benzofuran-5-yl), benzothiophene (e.g., benzo[b]thien-2-yl and benzo[b]thien-5-yl), benzimidazole, benzoxazole, benzothiazole, benzotriazole, quinoline (e.g., 2-quinolyl), isoquinoline, quinazoline, quinoxaline and the like.

Monovalent saturated heterocycles typically contain from 3 to 10 total ring atoms, of which 2 to 9 are ring carbon atoms, and 1 to 4 are ring heteroatoms, and include, for example —C₃₋₅heterocycle. Representative monovalent saturated heterocycles include, by way of example, monovalent species of pyrrolidine, imidazolidine, pyrazolidine, piperidine, 1,4-dioxane, morpholine, thiomorpholine, piperazine, 3-pyrroline and the like. In some instances, moieties may be described as being taken together to form a saturated —C₃₋₅heterocycle optionally containing an oxygen atom in the ring. Such groups include:

Monovalent partially unsaturated heterocycles typically contain from 3 to 10 total ring atoms, of which 2 to 11 are ring carbon atoms, and 1 to 3 are ring heteroatoms, and include, for example —C₃₋₅heterocycle and —C₂₋₁₂heterocycle. Representative monovalent partially unsaturated heterocycles include, by way of example, pyran, benzopyran, benzodioxole (e.g., benzo[1,3]dioxol-5-yl), tetrahydropyridazine, 2,5-dihydro-H-pyrrole, dihydroimidazole, dihydrotriazole, dihydrooxazole, dihydroisoxazole, dihydrothiazole, dihydroisothiazole, dihydrooxadiazole, dihydrothiadiazole, tetrahydropyridazine, hexahydropyrroloquinoxaline, and dihydrooxadiazabenzo[e]azulene. In some instances, moieties may be described as being taken together to form a partially unsaturated —C₃₋₅heterocycle. Such groups include:

The term “optionally substituted” means that group in question may be unsubstituted or it may be substituted one or several times, such as 1 to 3 times, or 1 to 5 times, or 1 to 8 times. For example, a phenyl group that is “optionally substituted” with halo atoms, may be unsubstituted, or it may contain 1, 2, 3, 4, or 5 halo atoms; and an alkyl group that is “optionally substituted” with fluoro atoms may be unsubstituted, or it may contain 1, 2, 3, 4, 5, 6, 7, or 8 fluoro atoms. Similarly, a group that is “optionally substituted” with one or two —C₁₋₆alkyl groups, may be unsubstituted, or it may contain one or two —C₁₋₆alkyl groups.

As used herein, the phrase “having the formula” or “having the structure” is not intended to be limiting and is used in the same way that the term “comprising” is commonly used. For example, if one structure is depicted, it is understood that all stereoisomer and tautomer forms are encompassed, unless stated otherwise.

The term “pharmaceutically acceptable” refers to a material that is not biologically or otherwise unacceptable when used in the invention. For example, the term “pharmaceutically acceptable carrier” refers to a material that can be incorporated into a composition and administered to a patient without causing unacceptable biological effects or interacting in an unacceptable manner with other components of the composition. Such pharmaceutically acceptable materials typically have met the required standards of toxicological and manufacturing testing, and include those materials identified as suitable inactive ingredients by the U.S. Food and Drug administration.

The term “pharmaceutically acceptable salt” means a salt prepared from a base or an acid which is acceptable for administration to a patient, such as a mammal (for example, salts having acceptable mammalian safety for a given dosage regime). However, it is understood that the salts covered by the invention are not required to be pharmaceutically acceptable salts, such as salts of intermediate compounds that are not intended for administration to a patient. Pharmaceutically acceptable salts can be derived from pharmaceutically acceptable inorganic or organic bases and from pharmaceutically acceptable inorganic or organic acids. In addition, when a compound of formula I contains both a basic moiety, such as an amine, pyridine or imidazole, and an acidic moiety such as a carboxylic acid or tetrazole, zwitterions may be formed and are included within the term “salt” as used herein. Salts derived from pharmaceutically acceptable inorganic bases include ammonium, calcium, copper, ferric, ferrous, lithium, magnesium, manganic, manganous, potassium, sodium, and zinc salts, and the like. Salts derived from pharmaceutically acceptable organic bases include salts of primary, secondary and tertiary amines, including substituted amines, cyclic amines, naturally-occurring amines and the like, such as arginine, betaine, caffeine, choline, N,N-dibenzylethylenediamine, diethylamine, 2-diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine, ethylenediamine, N-ethylmorpholine, N-ethylpiperidine, glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysine, methylglucamine, morpholine, piperazine, piperadine, polyamine resins, procaine, purines, theobromine, triethylamine, trimethylamine, tripropylamine, tromethamine and the like. Salts derived from pharmaceutically acceptable inorganic acids include salts of boric, carbonic, hydrohalic (hydrobromic, hydrochloric, hydrofluoric or hydroiodic), nitric, phosphoric, sulfamic and sulfuric acids. Salts derived from pharmaceutically acceptable organic acids include salts of aliphatic hydroxyl acids (for example, citric, gluconic, glycolic, lactic, lactobionic, malic, and tartaric acids), aliphatic monocarboxylic acids (for example, acetic, butyric, formic, propionic and trifluoroacetic acids), amino acids (for example, aspartic and glutamic acids), aromatic carboxylic acids (for example, benzoic, p-chlorobenzoic, diphenylacetic, gentisic, hippuric, and triphenylacetic acids), aromatic hydroxyl acids (for example, o-hydroxybenzoic, p-hydroxybenzoic, 1-hydroxynaphthalene-2-carboxylic and 3-hydroxynaphthalene-2-carboxylic acids), ascorbic, dicarboxylic acids (for example, fumaric, maleic, oxalic and succinic acids), glucoronic, mandelic, mucic, nicotinic, orotic, pamoic, pantothenic, sulfonic acids (for example, benzenesulfonic, camphosulfonic, edisylic, ethanesulfonic, isethionic, methanesulfonic, naphthalenesulfonic, naphthalene-1,5-disulfonic, naphthalene-2,6-disulfonic and p-toluenesulfonic acids), xinafoic acid, and the like.

As used herein, the term “prodrug” is intended to mean an inactive (or significantly less active) precursor of a drug that is converted into its active form in the body under physiological conditions, for example, by normal metabolic processes. Such compounds may not possess pharmacological activity at NEP, but may be administered orally or parenterally and thereafter metabolized in the body to form compounds that are pharmacologically active at NEP. Exemplary prodrugs include esters such as C₁₋₆alkylesters and aryl-C₁₋₆alkylesters. In one embodiment, the active compound has a free carboxyl and the prodrug is an ester derivative thereof, i.e., the prodrug is an ester such as —C(O)OCH₂CH₃. Such ester prodrugs are then converted by solvolysis or under physiological conditions to be the free carboxyl compound. The term is also intended to include certain protected derivatives of compounds of formula I that may be made prior to a final deprotection stage. Thus, all protected derivatives and prodrugs of compounds formula I are included within the scope of the invention.

The term “therapeutically effective amount” means an amount sufficient to effect treatment when administered to a patient in need thereof, that is, the amount of drug needed to obtain the desired therapeutic effect. For example, a therapeutically effective amount for treating hypertension is an amount of compound needed to, for example, reduce, suppress, eliminate, or prevent the symptoms of hypertension, or to treat the underlying cause of hypertension. In one embodiment, a therapeutically effective amount is that amount of drug needed to reduce blood pressure or the amount of drug needed to maintain normal blood pressure. On the other hand, the term “effective amount” means an amount sufficient to obtain a desired result, which may not necessarily be a therapeutic result. For example, when studying a system comprising a NEP enzyme, an “effective amount” may be the amount needed to inhibit the enzyme.

The term “treating” or “treatment” as used herein means the treating or treatment of a disease or medical condition (such as hypertension) in a patient, such as a mammal (particularly a human) that includes one or more of the following: (a) preventing the disease or medical condition from occurring, i.e., preventing the reoccurrence of the disease or medical condition or prophylactic treatment of a patient that is pre-disposed to the disease or medical condition; (b) ameliorating the disease or medical condition, i.e., eliminating or causing regression of the disease or medical condition in a patient; (c) suppressing the disease or medical condition, i.e., slowing or arresting the development of the disease or medical condition in a patient; or (d) alleviating the symptoms of the disease or medical condition in a patient. For example, the term “treating hypertension” would include preventing hypertension from occurring, ameliorating hypertension, suppressing hypertension, and alleviating the symptoms of hypertension (for example, lowering blood pressure). The term “patient” is intended to include those mammals, such as humans, that are in need of treatment or disease prevention or that are presently being treated for disease prevention or treatment of a specific disease or medical condition, as well as test subjects in which compounds of the invention are being evaluated or being used in an assay, for example an animal model.

All other terms used herein are intended to have their ordinary meaning as understood by those of ordinary skill in the art to which they pertain.

In one aspect, the invention relates to compounds of formula I:

or a pharmaceutically acceptable salt thereof.

As used herein, the term “compound of the invention” includes all compounds encompassed by formula I such as the species embodied in formulas Ia-Id, Ia-1 to Ia-10, Ib-1 to Ib-3, as well as the compounds encompassed by formulas II-X, and species thereof. Similarly, reference to compound of a given formula is intended to include all species; for example the term “compound of formula III” is intended to include the species IIIa and IIIb, and so forth. In addition, the compounds of the invention may also contain several basic or acidic groups (for example, amino or carboxyl groups) and therefore, such compounds can exist as a free base, free acid, or in various salt forms. All such salt forms are included within the scope of the invention. Furthermore, the compounds of the invention may also exist as prodrugs. Accordingly, those skilled in the art will recognize that reference to a compound herein, for example, reference to a “compound of the invention” or a “compound of formula I” includes a compound of formula I as well as pharmaceutically acceptable salts and prodrugs of that compound unless otherwise indicated. Further, the term “or a pharmaceutically acceptable salt and/or prodrug thereof” is intended to include all permutations of salts and prodrugs, such as a pharmaceutically acceptable salt of a prodrug. Furthermore, solvates of compounds of formula I are included within the scope of this invention.

The compounds of formula I may contain one or more chiral centers and therefore, these compounds may be prepared and used in various stereoisomeric forms. Accordingly, the invention also relates to racemic mixtures, pure stereoisomers (e.g., enantiomers and diastereoisomers), stereoisomer-enriched mixtures, and the like unless otherwise indicated. When a chemical structure is depicted herein without any stereochemistry, it is understood that all possible stereoisomers are encompassed by such structure. Thus, for example, the terms “compound of formula I,” “compounds of formula II,” and so forth, are intended to include all possible stereoisomers of the compound. Similarly, when a particular stereoisomer is shown or named herein, it will be understood by those skilled in the art that minor amounts of other stereoisomers may be present in the compositions of the invention unless otherwise indicated, provided that the utility of the composition as a whole is not eliminated by the presence of such other isomers. Individual stereoisomers may be obtained by numerous methods that are well known in the art, including chiral chromatography using a suitable chiral stationary phase or support, or by chemically converting them into diastereoisomers, separating the diastereoisomers by conventional means such as chromatography or recrystallization, then regenerating the original stereoisomer.

Additionally, where applicable, all cis-trans or E/Z isomers (geometric isomers), tautomeric forms and topoisomeric forms of the compounds of the invention are included within the scope of the invention unless otherwise specified. For example, if X is depicted as (R⁴ being hydrogen):

it is understood that the compound may also exist in a tautomeric form such as:

More specifically, compounds of formula I can contain at least two chiral centers when the “Z” moiety is —CH—, and at least one chiral center when the “Z” moiety is —N—, indicated by the symbols * and ** in the following formulas Ia and Ib:

The following structures are depicted with R^(2a) as —CH₂OH. In one stereoisomer of the compound of formula Ia, both carbon atoms identified by the * and ** symbols have the (R) configuration. This embodiment of the invention is shown in formula Ia-1 (for R^(2b)=H) and formula Ia-2 (for R^(2b)=—CH₃):

In this embodiment, compounds have the (R,R) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (R,R) configuration at these carbon atoms. In another stereoisomer of the compound of formula Ia, both carbon atoms identified by the * and ** symbols have the (S) configuration. This embodiment of the invention is shown in formula Ia-3 (for R^(2b)=H) and formula Ia-4 (for R^(2b)=—CH₃):

In this embodiment, compounds have the (S,S) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (S,S) configuration at these carbon atoms. In yet another stereoisomer of the compound of formula Ia, the carbon atom identified by the symbol * has the (S) configuration and the carbon atom identified by the symbol ** has the (R) configuration. This embodiment of the invention is shown in formula Ia-5 (for R^(2b)=H) and formula Ia-6 (for R^(2b)=—CH₃):

In this embodiment, compounds have the (S,R) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (S,R) configuration at these carbon atoms. In still another stereoisomer of the compound of formula Ia, the carbon atom identified by the symbol * has the (R) configuration and the carbon atom identified by the symbol ** has the (S) configuration. This embodiment of the invention is shown in formula Ia-7 (for R^(2b)=H) and formula Ia-8 (for R^(2b)=—CH₃):

In this embodiment, compounds have the (R,S) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (R,S) configuration at these carbon atoms.

The following structures are depicted with R^(2a) as —CH₂OH. In one stereoisomer of the compound of formula Ib, the carbon atom identified by the * symbol has the (R) configuration. This embodiment of the invention is shown in formula Ib-1:

In this embodiment, compounds have the (R) configuration at the * carbon atom or are enriched in a stereoisomeric form having the (R) configuration at this carbon atom. In another stereoisomer of the compound of formula Ib, the carbon atom identified by the * symbol has the (S) configuration. This embodiment of the invention is shown in formula Ib-2:

In this embodiment, compounds have the (S) configuration at the * carbon atom or are enriched in a stereoisomeric form having the (S) configuration at this carbon atom.

The following structures are depicted with R^(2a) and R^(2b) taken together to form —CH₂—O—CH₂—, thus, the carbon atom identified by the * symbol is not chiral. In one stereoisomer of the compound of formula Ia, the carbon atom identified by the ** symbol has the (R) configuration and I another stereoisomer, the carbon atom identified by the ** symbol has the (S) configuration, shown in formulas Ia-9 and formula Ia-10, respectively:

When R^(2a) and R^(2b) taken together to form —CH₂—O—CH₂— and Z is —N—, then the formula can be achiral, as shown in formula Ib-3:

In some embodiments, in order to optimize the therapeutic activity of the compounds of the invention, e.g., to treat hypertension, it may be desirable that the carbon atoms identified by the * and ** symbols have a particular configuration or are enriched in a stereoisomeric form having such configuration. Thus, in certain aspects, this invention relates to each individual enantiomer or to an enantiomer-enriched mixture of enantiomers comprising predominately one enantiomer or the other enantiomer. In other embodiments, the compounds of the invention are present as racemic mixtures of enantiomers.

The compounds of the invention, as well as those compounds used in their synthesis, may also include isotopically-labeled compounds, that is, where one or more atoms have been enriched with atoms having an atomic mass different from the atomic mass predominately found in nature. Examples of isotopes that may be incorporated into the compounds of formula I, for example, include, but are not limited to, ²H, ³H, ¹³C, ¹⁴C, ¹⁵N, ¹⁸O, ¹⁷O, ³⁵S, ³⁶C, and ¹⁸F. Of particular interest are compounds of formula I enriched in tritium or carbon-14 which can be used, for example, in tissue distribution studies; compounds of formula I enriched in deuterium especially at a site of metabolism resulting, for example, in compounds having greater metabolic stability; and compounds of formula I enriched in a positron emitting isotope, such as ¹¹C, ¹⁸F, ¹⁵O and ¹³N, which can be used, for example, in Positron Emission Topography (PET) studies.

The nomenclature used herein to name the compounds of the invention is illustrated in the Examples herein. This nomenclature has been derived using the commercially available AutoNom software (MDL, San Leandro, Calif.).

Representative Embodiments

The following substituents and values are intended to provide representative examples of various aspects and embodiments of the invention. These representative values are intended to further define and illustrate such aspects and embodiments and are not intended to exclude other embodiments or to limit the scope of the invention. In this regard, the representation that a particular value or substituent is preferred is not intended in any way to exclude other values or substituents from the invention unless specifically indicated.

In one aspect, this invention relates to compounds of formula I:

R¹ is selected from —OR⁷ and —NR⁸R⁹. The R⁷ moiety is selected from:

H;

—C₁₋₈alkyl, e.g., —CH₃, —CH₂CH₃, —(CH₂)₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₄CH₃, —(CH₂)₂CH(CH₃)₂, —(CH₂)₅CH₃, and —(CH₂)₆CH₃;

—C₁₋₃alkylene-C₆₋₁₀aryl, e.g., benzyl;

—C₁₋₃alkylene-C₁₋₉heteroaryl, e.g., —CH₂-pyridinyl and —(CH₂)-2-pyridinyl;

—C₃₋₇cycloalkyl, e.g., cyclopentyl;

—[(CH₂)₂O]₁₋₃CH₃, e.g., —(CH₂)₂OCH₃ and —[(CH₂)₂O]₂CH₃;

—C₁₋₆alkylene-OC(O)R¹⁰, e.g., —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂CH(CH₃)OC(O)CH₂CH₃, —CH₂OC(O)OCH₃, —CH₂OC(O)OCH₂CH₃, —CH(CH₃)OC(O)OCH₂CH₃, —CH(CH₃)OC(O)O—CH(CH₃)₂, —CH₂CH(CH₃)OC(O)-cyclopentyl, —CH₂OC(O)O-cyclopropyl, —CH(CH₃)—OC(O)—O-cyclohexyl, —CH₂OC(O)O-cyclopentyl, —CH₂CH(CH₃)OC(O)-phenyl, —CH₂OC(O)O-phenyl, —CH₂OC(O)—CH[CH(CH₃)₂]—NH₂, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)OCH₃, and —CH(CH₃)OC(O)—CH(NH₂)CH₂COOCH₃;

—C₁₋₆alkylene-NR¹²R¹³, e.g., —(CH₂)₂—N(CH₃)₂,

—C₁₋₆alkylene-C(O)R³¹, e.g., —CH₂C(O)OCH₃, —CH₂C(O)O-benzyl, —CH₂C(O)—N(CH₃)₂, and

—C₀₋₆alkylenemorpholinyl, e.g., —(CH₂)₂-morpholinyl and —(CH₂)₃-morpholinyl:

—C₁₋₆alkylene-SO—C₁₋₆alkyl, e.g., —(CH₂)₂SO₂CH₃;

for example,

The R¹⁰ moiety is selected from:

—C₁₋₆alkyl, e.g., —CH₃ and —CH₂CH₃;

—O—C₁₋₆alkyl, e.g., —OCH₃, —O—CH₂CH₃, and —O—CH(CH₃)₂;

—C₃₋₇cycloalkyl, e.g., cyclopentyl;

—O—C₃₋₇cycloalkyl, e.g., —O-cyclopropyl, —O-cyclohexyl, and —O-cyclopentyl;

phenyl;

—O-phenyl;

—NR¹²R¹³;

—CH[CH(CH₃)₂]—NH₂;

—CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, e.g., —CH[CH(CH₃)₂]—NHC(O)OCH₃; and

—CH(NH₂)CH₂COOCH₃.

The R¹² and R¹³ moieties are independently selected from H, —C₁₋₄alkyl (e.g., CH₃), and benzyl. Alternately, the R¹² and R¹³ moieties can be taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—, for example to form a group such as:

The R³¹ moiety is selected from —O—C₁₋₆alkyl, e.g., —OCH₃, —O-benzyl, and —NR¹²R¹³, e.g., —N(CH₃)₂, and

The R³² moiety is —C₁₋₆alkyl (e.g., —CH₃ and —C(CH₃)₃) or —C₀₋₆alkylene-C₆₋₁₀aryl.

The R⁸ moiety is selected from:

H;

—OH;

—OC(O)R¹⁴, e.g., —OC(O)CH₃, —OC(O)-phenyl, —OC(O)—OCH₂-phenyl, —OC(O)—CH₂O-phenyl, —OC(O)(NH₂), and —OC(O)[N(CH₃)₂;

—CH₂COOH;

—O-benzyl;

pyridyl; and

—OC(S)NR¹⁵R¹⁶, e.g., —OC(S)NH₂ and —OC(S)N(CH₃)₂.

The R¹⁴ moiety is selected from:

H;

—C₁₋₆alkyl, e.g., —CH₃;

—C₆₋₁₀aryl, e.g., phenyl;

—OCH₂—C₆₋₁₀aryl, e.g., —OCH₂-phenyl;

—CH₂O—C₆₋₁₀aryl, e.g., —CH₂O-phenyl; and

—NR¹⁵R¹⁶, e.g., —NH₂ and N(CH₃)₂.

The R¹⁵ and R¹⁶ moieties are independently selected from H and —C₁₋₄alkyl.

The R⁹ is moiety selected from H, —C₁₋₆alkyl (e.g., —CH₃), and —C(O)R¹⁷ (e.g., —C(O)H). The R¹⁷ moiety is selected from H, —C₁₋₆alkyl (e.g., —CH₂CH₃), —C₃₋₇cycloalkyl (e.g., cyclopropyl), —C₆₋₁₀aryl (e.g., phenyl), and —C₁₋₉heteroaryl (e.g., pyridine).

In addition, each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms. For example, when R¹ is —OR⁷ and R⁷ is —C₁₋₈alkyl, R¹ can also be a group such as —OCH(CH₃)CF₃, —OCH₂CF₂CF₃, —OCH(CF₃)₂, —O(CH₂)₂CF₃, —OCH(CH₂F)₂, —OC(CF₃)₂CH₃, and —OCH(CH₃)CF₂CF₃.

In one embodiment, R¹ is —OR⁷; R⁷ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl; —O—C₃₋₇cycloalkyl, —CH[CH(CH₃)₂]—NH₂, and —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl; R¹² and R¹³ are —C₁₋₆alkyl or are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³¹ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —CH₃. In other embodiments these compounds have formulas III-X.

In one embodiment, R¹ is selected from —OR⁷ and —NR⁸R⁹, R⁷ is H, R⁸ is H or —OH, and R⁹ is H. In other embodiments these compounds have formulas III-X.

In another embodiment, R¹ is —OR⁷, where R⁷ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₁₋₆alkylenemorpholinyl; —C₁₋₆alkylene-SO₂—C₁₋₆alkyl;

In yet another embodiment, R¹ is —NR⁸R⁹; where R⁸ is selected from —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is H. In yet another embodiment, R¹ is —NR⁸R⁹, where R⁸ is H or —OH; and R⁹ is —C₁₋₆alkyl or —C(O)R¹⁷. In yet another embodiment, R¹ is —NR⁸R⁹, where R⁸ is selected from —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is —C₁₋₆alkyl or —C(O)R¹⁷. In other embodiments these compounds have formulas III-X. In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. For example, in one embodiment, R¹ is —OR⁷ and R⁷ is —C₁₋₆alkylene-OC(O)R¹⁰, such as —O—CH(CH₃)OC(O)—O-cyclohexyl:

making the compound a cilexetil ester; or R¹ is —OR⁷ and R⁷ is −C₀₋₆alkylenemorpholinyl such as —O—(CH₂)-2-morpholinyl:

making the compound a 2-morpholinoethyl or mofetil ester; or R¹ is —OR⁷ and R⁷ is

such as —O—CH₂-5-methyl-[1,3]dioxol-2-one:

making the compound a medoxomil ester.

The “Z” moiety is —CH— or —N—. In one embodiment, Z is —CH— and in another embodiment Z is —N—.

The R^(2a) moiety can be —CH₂OH, —CH₂OP(O)(OH)₂, or —CH₂OC(O)CH(R³⁷)NH₂, where R³⁷ is selected from H, —CH(CH₃)₂, phenyl, and benzyl. Alternately, R^(2a) can be taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹— or taken together with R⁸ to form —CH₂OO—C(O)—. The R^(2b) moiety is selected from H and —CH₃. Alternately, the R^(2b) moiety can be taken together with R^(2a) to form —CH₂—O—CH₂—. R¹⁸ and R¹⁹ are independently selected from H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or R¹⁸ and R¹⁹ are taken together to form ═O.

In one embodiment, R^(2a) is —CH₂OH and R^(2b) is H. In another embodiment, R^(2a) is —CH₂OH and R^(2b) is —CH₃. These can be depicted as formulas III and IV, respectively:

In one embodiment Z is —CH—, R^(2a) is —CH₂OH, and R^(2b) is H, and in another embodiment Z is —CH—, R^(2a) is —CH₂OH, and R^(2b) is —CH₃. These embodiments can be depicted as formulas IIIa and IVa, respectively:

In another embodiment Z is —N—, R^(2a) is —CH₂OH, and R^(2b) is H, and in another embodiment Z is —N—, R^(2a) is —CH₂OH, and R^(2b) is —CH₃. These embodiments can be depicted as formulas IIIb and IVb, respectively:

In another embodiment, R^(2a) is —CH₂OP(O)(OH)₂ and R^(2b) is H. In another embodiment, R^(2a) is —CH₂OP(O)(OH)₂ and R^(2b) is —CH₃. These can be depicted as formulas V and VI, respectively:

In one embodiment Z is —CH—, R^(2a) is —CH₂OP(O)(OH)₂, and R^(2b) is H, and in another embodiment Z is —CH—, R^(2a) is —CH₂OP(O)(OH)₂, and R^(2b) is —CH₃. These embodiments can be depicted as formulas Va and VIa, respectively:

In another embodiment Z is —N—, R^(2a) is —CH₂OP(O)(OH)₂, and R^(2b) is H, and in another embodiment Z is —N—, R^(2a) is —CH₂OP(O)(OH)₂, and R^(2b) is —CH₃. These embodiments can be depicted as formulas Vb and VIb, respectively:

In one embodiment Z is —CH—, R^(2a) is —CH₂OC(O)CH(R³⁷)NH₂, and R^(2b) is H, and in another embodiment Z is —CH—, R^(2a) is —CH₂OC(O)CH(R³⁷)NH₂, and R^(2b) is —CH₃. These embodiments can be depicted as formulas VIIa and VIIIa, respectively:

In another embodiment Z is —N—, R^(2a) is —CH₂OC(O)CH(R³⁷)NH₂, and R^(2b) is H, and in another embodiment Z is —N—, R^(2a) is —CH₂OC(O)CH(R³⁷)NH₂, and R^(2b) is —CH₃. These embodiments can be depicted as formulas VIIb and VIIIb, respectively:

In still another embodiment, the R^(2a) and R^(2b) moieties are taken together to form —CH₂—O—CH₂—. This can be depicted as formula IX:

In one embodiment Z is —CH— and R^(2a) and R^(2b) are taken together to form —CH₂—O—CH₂—, and in another embodiment Z is —CH— and R^(2a) and R^(2b) are taken together to form —CH₂—O—CH₂—. These embodiments can be depicted as formulas IXa and IXb respectively:

In other embodiments, R^(2a) can be taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹— or taken together with R⁸ to form —CH₂O—C(O)—. When R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—, this embodiment can be depicted as:

and in one embodiment, R¹⁸ and R¹⁹ are independently H or —C₁₋₆alkyl, and R^(2b) is —CH₃. When R¹⁸ and R¹⁹ are taken together to form ═O, this embodiment can be depicted as:

When R^(2a) is taken together with R⁸ to form —CH₂O—C(O)—, this embodiment can be depicted as:

In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. Compounds where R^(2a) is —CH₂OP(O)(OH)₂ may also find utility as prodrugs.

The “Z” moiety is —CH— or —N—, which can be depicted as formulas Ic and Id, respectively:

The “X” moiety is a —C₁₋₉heteroaryl, and the point of attachment is at any available carbon or nitrogen ring atom. Note that in some embodiments, R³ and/or R⁴ may be absent. When present, R³ is on any available carbon atom. When present, R⁴ is on any available carbon atom or nitrogen atom. Exemplary —C₁₋₉heteroaryl rings include, by way of illustration and not limitation:

pyrazole rings such:

specific examples of which include:

imidazole rings such as:

specific examples of which include:

triazole rings, including 1,2,3-triazoles such as:

as well as 1,2,4-triazoles such as:

benzotriazole rings such as:

specific examples of which include:

furan rings:

specific examples of which include:

pyrrole rings:

specific examples of which include:

tetrazole rings such as:

pyrazine rings:

a specific example of which includes:

thiophene rings:

specific examples of which include:

oxazole rings:

specific examples of which include:

isoxazole rings:

specific examples of which include:

thiazole rings:

specific example of which include:

isothiazole rings:

oxadiazole rings, including [1,2,4]oxadiazoles such as:

as well as [1,2,3]oxadiazoles such as

and [1,3,4]oxadiazoles:

thiadiazole rings, including [1,2,4]thiadiazoles such as:

as well as [1,2,3]thiadiazoles such as:

and [1,3,4]thiadiazoles:

pyridazine rings:

pyridine rings:

specific examples of which include:

pyrimidine rings:

specific examples of which include:

pyran rings such as:

benzimidazole rings such as:

specific examples of which include:

benzoxazole rings such as:

specific examples of which include:

benzothiazole rings such as:

specific examples of which include:

pyridylimidazole rings such as:

a specific example of which includes:

pyridyltriazole rings such as:

specific examples of which include:

In one particular embodiment, X is selected from pyrazole, imidazole, triazole, benzotriazole, furan, pyrrole, tetrazole, pyrazine, thiophene, oxazole, isoxazole, thiazole, isothiazole, oxadiazole, thiadiazole, pyridazine, pyridine, pyrimidine, pyran, benzimidazole, benzoxazole, benzothiazole, pyridylimidazole, and pyridyltriazole. In other embodiments these compounds have formulas III-IX.

It is understood that some —C₁₋₉heteroaryl rings can exist in a tautomeric form, and that such tautomeric forms are part of the invention and are encompassed by the term “heteroaryl.” Therefore, if a compound is depicted with a —C₁₋₉heteroaryl ring, it is understood that the compound can also exist in a tautomeric form and vice versa, and that both forms are covered by the invention.

—C₁₋₉ heteroaryl ring exemplary ring exemplary tautomer(s) pyrazole

imidazole

triazole

oxazole

thiazole

isothiazole

oxadiazole

thiadiazole

pyridazine

In one particular embodiment, X is selected from pyrazole, imidazole, triazole, benzotriazole, oxazole, isoxazole, pyrimidine, pyridazine, benzimidazole, pyran, and pyridyltriazole. In other embodiments these compounds have formulas III-VIII. In still another embodiment X is triazole, and in one specific embodiment, have formula X:

where Z, R¹, R^(2a), R^(2b), R³-R⁶, a, and b are as defined for formula I. In yet another embodiment, the compounds of the invention have formula Xa:

where Z, R¹, R^(2b), R³-R⁶, a, and b are as defined for formula I. In yet another embodiment, the compounds of the invention have formula Xb:

where R¹, R³-R⁶, a, and b, are as defined for formula I. In still another embodiment, the compounds of the invention have formula Xc:

where R¹, R⁵-R⁶, a, and b, are as defined for formula I. In still another embodiment, the compounds of the invention have formula Xd:

where R¹, R⁵-R⁶, a, and b, are as defined for formula I.

The R³ moiety can be absent. When present, R³ is attached to a carbon atom in the “X” group, and is selected from:

H;

halo, e.g., chloro and fluoro;

—C₀₋₅alkylene-OH, e.g., —OH, —CH₂OH, —CH(OH)CH₃, and —C(CH₃)₂—OH;

—NH₂;

—C₁₋₆alkyl, e.g., —CH₃, —(CH₂)₂CH₃, —CH(CH₃)₂, and —(CH₂)₃—CH₃;

—CF₃;

—C₃₋₇cycloalkyl, e.g., cyclopropyl and cyclohexyl;

—C₀₋₂alkylene-O—C₁₋₆alkyl, e.g., —OCH₃, —OCH₂CH₃, —CH₂—OCH₃, and —(CH₂)₂—OCH₃;

—C(O)R²⁰, e.g., —C(O)H and —C(O)CH₃;

—C₀₋₁alkylene-COOR²¹, e.g., —COOH, —CH₂—COOH, —C(O)O—CH₂CH₃, —C(O)O—(CH₂)₂OCH₃—C(O)O—CH₂OC(O)CH₃, —CH₂—C(O)O—CH₂OC(O)CH₃, —C(O)O—CH₂OC(O)O—CH₃, —CH₂—C(O)O—CH₂OC(O)O—CH₃, —C(O)O—CH(CH₃)OC(O)O—CH₂CH₃, —C(O)O—CH(CH₃)OC(O)O—CH(CH(CH₃)₂, —C(O)O—CH₂CH(CH₃)OC(O)-cyclopentyl, —C(O)O—CH₂OC(O)O-cyclopropyl, —C(O)O—CH(CH₃)—OC(O)—O-cyclohexyl, —C(O)O—CH₂OC(O)O-cyclopentyl, —C(O)O—CH₂CH(CH₃)OC(O)-phenyl, —C(O)O—CH₂OC(O)O-phenyl, —C(O)O—CH₂-pyridine, —C(O)O—CH₂-pyrrolidine, —C(O)O—(CH₂)₂-morpholinyl, —C(O)O—(CH₂)₃-morpholinyl, and —C(O)O—(CH₂)₂—SO₂—CH₃;

—C(O)NR²²R²³, e.g., —C(O)NH₂, —C(O)NHCH₃, —C(O)N(CH₃)₂, —C(O)NH—(CH₂)₂CH₃, —C(O)NH—CH₂COOH, —C(O)NH—(CH₂)₂—OH, —C(O)NH—(CH₂)₂—N(CH₃)₂, —C(O)NH-cyclopropyl, —C(O)NH—(CH₂)₂-imidazolyl, —C(O)N(CH₃)—CH₂CH(CH₃)₂, and —C(O)N(CH₃)[(CH₂)₂OCH₃];

—NHC(O)R²⁴, e.g., —NHC(O)—CH₂CH₃, —NHC(O)—(CH₂)₃CH₃, —NHC(O)O—CH₂CH₃, —NHC(O)—CH₂—OCH₃, —NHC(O)-2-methoxyphenyl, —NHC(O)-2-chlorophenyl, and —NHC(O)-2-pyridine;

═O;

—NO₂;

—C(CH₃)═N(OH);

phenyl optionally substituted with one or two groups independently selected from halo, —OH, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl (e.g., phenyl, 2-chlorophenyl, 2-fluorophenyl, 2-hydroxyphenyl, 2-trifluoromethylphenyl, 2-methoxyphenyl, 3-chlorophenyl, 3-fluorophenyl, 3-methoxyphenyl, 3-NHC(O)CH₃-phenyl, 4-chlorophenyl, 4-fluorophenyl, 4-methoxyphenyl, 4-biphenyl, 2,5-dichlorophenyl, 2,5-dimethoxyphenyl, 2,4-dichlorophenyl, 2-methoxy, 5-fluorophenyl, and 3,4-dichlorophenyl);

naphthalenyl;

pyridinyl;

pyrazinyl;

pyrazolyl optionally substituted with methyl;

thiophenyl optionally substituted with methyl or halo (e.g., chloro);

furanyl; and

—CH₂-morpholinyl.

The R²⁰ moiety is selected from H and —C₁₋₆alkyl (e.g., —CH₃). The R²¹ moiety is selected from:

H;

—C₁₋₆alkyl, e.g., —CH₃ and —CH₂CH₃;

—C₁₋₃alkylene-C₆₋₁₀aryl;

—C₁₋₃alkylene-C₁₋₉heteroaryl, e.g., —CH₂-pyridine;

—C₃₋₇cycloalkyl;

—[(CH₂)₂O]₁₋₃CH₃, e.g., —(CH₂)₂OCH₃;

—C₁₋₆alkylene-OC(O)R²⁵, e.g., —CH₂OC(O)CH₃, —CH₂OC(O)O—CH₃, —CH₂OC(O)O—CH₃, —CH(CH₃)OC(O)O—CH₂CH₃, —CH(CH₃)OC(O)O—CH(CH₃)₂, —CH₂CH(CH₃)OC(O)-cyclopentyl, —CH₂OC(O)O-cyclopropyl, —CH(CH₃)—OC(O)—O-cyclohexyl, —CH₂OC(O)O-cyclopentyl, —CH₂CH(CH₃)OC(O)-phenyl, and —CH₂OC(O)O-phenyl;

—C₁₋₆alkylene-NR²⁷R²⁸, e.g., —CH₂-pyrrolidine;

—C₁₋₆alkylene-C(O)R³³;

—C₀₋₆alkylenemorpholinyl, e.g., —(CH₂)₂-morpholinyl and —(CH₂)₃-morpholinyl:

—C₁₋₆alkylene-SO₂—C₁₋₄alkyl, e.g., —(CH₂)₂—SO₂—CH₃;

The R²² and R²³ moieties are independently selected from:

H;

—C₁₋₆alkyl, e.g., —CH₃ and —(CH₂)₂CH₃;

—CH₂COOH;

—(CH₂)₂OH;

—(CH₂)₂OCH₃;

—(CH₂)₂SO₂NH₂;

—(CH₂)₂N(CH₃)₂;

—C₀₋₁alkylene-C₃₋₇cycloalkyl, e.g., cyclopropyl and —CH₂-cyclopropyl; and

—(CH₂)₂-imidazolyl.

R²² and R²³ may also be taken together to form a saturated or partially unsaturated —C₃₋₅heterocycle optionally substituted with halo, —OH, —COOH, or —CONH₂, and optionally containing an oxygen atom in the ring. Saturated —C₃₋₅heterocycles include azetidine, pyrrolidine, piperidine and morpholine, such that exemplary R³ groups include:

Partially unsaturated —C₃₋₅heterocycles include 2,5-dihydro-1H-pyrrole, such that exemplary R³ groups include:

The R²⁴ moiety is selected from:

—C₁₋₆alkyl, e.g., —CH₂CH₃ and —(CH₂)₃CH₃;

—C₀₋₁alkylene-O—C₁₋₆alkyl, e.g., —O—CH₂CH₃ and —CH₂—OCH₃;

phenyl optionally substituted with halo or —OCH₃, e.g., -2chlorophenyl or -2-methoxyphenyl; and

—C₁₋₉heteroaryl, e.g., 2-pyridine.

R²⁵ is selected from:

—C₁₋₆alkyl, e.g., —CH₃, —CH₂CH₃, and —(CH₂)₃CH₃;

—O—C₁₋₆alkyl, e.g., —OCH₃, —OCH₂CH₃, and —OCH(CH₃)₂;

—C₃₋₇cycloalkyl, e.g., cyclopentyl;

—O—C₃₋₇cycloalkyl, e.g., —O-cyclopropyl, —O-cyclopentyl, and —O-cyclohexyl;

phenyl;

—O-phenyl;

—NR²⁷R²⁸;

—CH[CH(CH₃)₂]—NH₂;

—CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, e.g., —CH[CH(CH₃)₂]—NHC(O)OCH₃; and

—CH(NH₂)CH₂COOCH₃.

R²⁷ and R²⁸ are independently selected from H, —C₁₋₆alkyl, and benzyl, or R²⁷ and R²⁸ are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂—O—(CH₂)₂—; R³³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR²⁷R²⁸; and R³⁴ is —C₁₋₆alkyl (e.g., —CH₃ and —C(CH₃)₃) or —C₀₋₆alkylene-C₆₋₁₀aryl.

In addition, each alkyl group in R³ is optionally substituted with 1 to 8 fluoro atoms. For example, when R³ is —C₀₋₁alkylene-COOR²¹ and R²¹ is —C₁₋₆alkyl, R³ can also be a group such as —COOCH(CH₃)CF₃, —COOCH₂CF₂CF₃, —COOCH(CF₃)₂, —COO(CH₂)₂CF₃, —COOCH(CH₂F)₂, —COOC(CF₃)₂CH₃, and —COOCH(CH₃)CF₂CF₃.

In one embodiment, R³ is selected from H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²⁰ is —C₁₋₆alkyl; R²¹ is H; and R²² and R²³ are independently selected from —C₁₋₆alkyl, —(CH₂)₂OCH₃, and —C₃₋₇cycloalkyl; or R²² and R²³ are taken together to form a saturated —C₃₋₅heterocycle. In other embodiments these compounds have formulas III-X.

In one embodiment, R³ is absent or is selected from H; halo; —C₀₋₅alkylene-OH; —NH₂; —C₁₋₆alkyl; —CF₃; —C₃₋₇cycloalkyl; —C₀₋₂alkylene-O—C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; —NHC(O)R²⁴; ═O; —NO₂; —C(CH₃)═N(OH); phenyl optionally substituted with one or two groups independently selected from halo, —OH, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl; naphthalenyl; pyridinyl; pyrazinyl; pyrazolyl optionally substituted with methyl; thiophenyl optionally substituted with methyl or halo; furanyl; and —CH₂-morpholinyl; and R²¹ is H. In other embodiments these compounds have formulas III-X.

In another embodiment, R³ is —C₀₋₁alkylene-COOR²¹, and R²¹ is selected from —C₁₋₆alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₇heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R²⁵; —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. In other embodiments these compounds have formulas III-X.

The R⁴ moiety can be absent. When present, R⁴ is attached to a carbon or nitrogen atom in the “X” group, and is selected from:

H;

—OH;

—C₁₋₆alkyl, e.g., —CH₃;

—C₁₋₂alkylene-COOR³⁵, e.g., —CH₂COOH and —(CH₂)₂—COOH;

—CH₂OC(O)CH(R³⁶)NH₂, e.g., —CH₂OC(O)CH[CH(CH₃)₂]NH₂;

—OCH₂OC(O)CH(R³⁶)NH₂, e.g., —OCH₂OC(O)CH[CH(CH₃)₂]NH₂;

—OCH₂OC(O)CH₃;

—CH₂OP(O)(OH)₂;

—CH₂CH(OH)CH₂OH;

—CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl;

pyridinyl; and

phenyl or benzyl optionally substituted with one or more groups selected from halo, —COOR³⁵, —OCH₃, —OCF₃, and —SCF₃ (e.g., 4-chlorophenyl, 3-methoxyphenyl, 2,4-dichlorophenyl, 3,4-dichlorophenyl, 2-chloro, 5-fluorophenyl, 3-trifluoromethoxy, 4-chlorophenyl, 3-trifluoromethylsulfanyl, 4-chlorophenyl, 2,6-difluoro, 4-chlorophenyl, 2-chlorobenzyl, 3-chlorobenzyl, 4-chlorobenzyl, 3-carboxybenzyl, 4-carboxybenzyl, 3-methoxybenzyl, 2-chloro, 5-fluorobenzyl, 3-chloro, 5-fluorobenzyl, 2-fluoro, 4-chlorobenzyl, 3-chloro, 4-fluorobenzyl, 3-OCF3, 4-chlorobenzyl, 3-SCF3, 4-chlorobenzyl, 2,6-difluoro, 3-chlorobenzyl, 2,6-difluoro, 4-chlorobenzyl, and 2,3,5,6-tetrafluoro, 4-methoxy benzyl).

The R³⁵ moiety is selected from:

H;

—C₁₋₆alkyl, e.g., —CH₃ and —CH₂CH₃;

—C₁₋₃alkylene-C₆₋₁₀aryl;

—C₁₋₃alkylene-C₁₋₉heteroaryl, e.g., —CH₂-pyridine;

—C₃₋₇cycloalkyl;

—[(CH₂)₂O]₁₋₃CH₃, e.g., —(CH₂)₂OCH₃;

—C₁₋₆alkylene-OC(O)R²⁵, e.g., —CH₂OC(O)CH₃, —CH₂OC(O)O—CH₃, —CH₂OC(O)O—CH₃, —CH(CH₃)OC(O)O—CH₂CH₃, —CH(CH₃)OC(O)O—CH(CH₃)₂, —CH₂CH(CH₃)OC(O)-cyclopentyl, —CH₂OC(O)O-cyclopropyl, —CH(CH₃)—OC(O)—O-cyclohexyl, —CH₂OC(O)O-cyclopentyl, —CH₂CH(CH₃)OC(O)-phenyl, and —CH₂OC(O)O-phenyl;

—C₁₋₆alkylene-NR²⁷R²⁸, e.g., —CH₂-pyrrolidine;

—C₁₋₆alkylene-C(O)R³³;

—C₀₋₆alkylenemorpholinyl, e.g., —(CH₂)₂-morpholinyl and —(CH₂)₃-morpholinyl:

−C₁₋₆alkylene-SO₂—C₁₋₆alkyl, e.g., —(CH₂)₂—SO₂—CH₃;

The R²⁵, R²⁷, R²⁸, R³³, and R³⁴ moieties are defined above. The R³⁶ moiety is selected from H, —CH(CH₃)₂, phenyl, and benzyl.

In addition, each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms. For example, when R⁴ is —C₁₋₂alkylene-COOR³⁵ and R³⁵ is —C₁₋₆alkyl, R⁴ can also be a group such as —COOCH(CH₃)CF₃, —COOCH₂CF₂CF₃, —COOCH(CF₃)₂, —COO(CH₂)₂CF₃, —COOCH(CH₂F)₂, —COOC(CF₃)₂CH₃, and —COOCH(CH₃)CF₂CF₃.

The R⁴ moiety can also be taken together with R³ to form -phenylene-O—(CH₂)₁₋₃— or -phenylene-O—CH₂—CHOH—CH₂—. For purposes of illustration only, these embodiments are depicted below with X being pyrazole. It is understood that other X groups can be used also.

In another particular embodiment, R⁴ is selected from H, —OH, —C₁₋₆alkyl, —CH₂OC(O)CH(R³⁶)NH₂, —CH₂OP(O)(OH)₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and benzyl. In other embodiments these compounds have formulas III-X.

In one embodiment, R⁴ is absent or is selected from H; —OH; —C₁₋₆alkyl; —C₁₋₂alkylene-COOR³⁵; —CH₂OC(O)CH(R³⁶)NH₂; —CH₂CH(OH)CH₂OH; pyridinyl; and phenyl or benzyl optionally substituted with one or more groups selected from halo, —COOR³⁵, —OCH₃, —OCF₃, and —SCF₃; and R³⁵ is H. In other embodiments these compounds have formulas III-X.

In another embodiment, R⁴ is selected from —OCH₂OC(O)CH₃; —CH₂OP(O)(OH)₂; —C₁₋₂alkylene-COOR³⁵; and phenyl or benzyl substituted with at least one —COOR³⁵ group; where R³⁵ is selected from —C₁₋₆alkyl, —C₁₋₃alkylene-C₁₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R²⁵; —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. In other embodiments these compounds have formulas III-X.

The numbering for the R⁵ and R⁶ groups is as follows:

The integer “a” is 0 or 1. The R⁵ moiety, when present, is selected from halo, —CH₃, —CF₃, and —CN. In one embodiment, a is 0. In another embodiment, a is 1, and R⁵ is halo, such as 3-chloro or 3-fluoro. The integer “b” is 0 or an integer from 1 to 3. The R⁶ moiety, when present, is independently selected from halo, —OH, —CH₃, —OCH₃, and —CF₃. In one embodiment, b is 0. In another embodiment, b is 1 and R⁶ is selected from Cl, F, —OH, —CH₃, —OCH₃, and —CF₃, such 2′-chloro, 3′-chloro, 2′-fluoro, 3′-fluoro, 2′-hydroxy, 3′-hydroxy, 3′-methyl, 2′-methoxy, or 3′-trifluoromethyl. In another embodiment, b is 1 and R⁶ is halo, —CH₃, or —OCH₃, such 3′-chloro, 3′-methyl, or 2′-methoxy. In one embodiment, b is 2 and R⁶ is 2′-fluoro-5′-chloro, 2′,5′-dichloro, 2′,5′-difluoro, 2′-methyl-5′-chloro, 3′-fluoro-5′-chloro, 3′-hydroxy-5′-chloro, 3′,5′-dichloro, 3′,5′-difluoro, 2′-methoxy-5′-chloro, 2′-methoxy-5′-fluoro, 2′-hydroxy-5′-fluoro, 2′-fluoro-3′-chloro, 2′-hydroxy-5′-chloro, or 2′-hydroxy-3′-chloro; and in another embodiment, b is 2 and each R⁶ is independently halo, for example, 2′-fluoro-5′-chloro and 2′,5′-dichloro. In another embodiment, b is 3 and each R⁶ is independently halo or —CH₃, such as 2′-methyl-3′,5′-dichloro or 2′-fluoro-3′-methyl-5′-chloro. In yet another embodiment, a is 1 and b is 1 and R⁵ and R⁶ are independently halo, for example, 3-chloro and 3′chloro. In other embodiments these compounds have formulas III-X. Of particular interest are compounds of the formulas:

The methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl. For example, in one embodiment, the methylene linker on the biphenyl is unsubstituted; in another embodiment, the methylene linker on the biphenyl is substituted with one —C₁₋₆alkyl group (e.g., —CH₃); and in yet another embodiment, the methylene linker on the biphenyl is substituted with two —C₁₋₆alkyl groups (e.g., two —CH₃ groups); in another embodiment, the methylene linker on the biphenyl is substituted with a cyclopropyl group. These embodiments are depicted, respectively, as:

In another embodiment, R¹ is —OR⁷; R⁷ is selected from H, —C₁₋₈alkyl, —C₁₋₃-alkylene-C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂−C₁₋₆alkyl,

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl; —O—C₃₋₇cycloalkyl, —CH[CH(CH₃)₂]—NH₂, and —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl; R¹² and R¹³ are —C₁₋₆alkyl or are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³¹ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —CH₃; R^(2a) is —CH₂OH and R^(2b) is H; or R^(2a) is selected from —CH₂OH, —CH₂OP(O)(OH)₂, and —CH₂OC(O)CH(R³⁷)NH₂, R^(2b) is —CH₃, and R³⁷ is —CH(CH₃)₂; or R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—, R¹⁸ and R¹⁹ are independently selected from H and —C₁₋₆alkyl, and R^(2b) is —CH₃; Z is —CH—; X is selected from pyrazole, triazole, benzotriazole, oxazole, isoxazole, pyrimidine, benzimidazole, and pyridyltriazole; R³ is selected from H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²⁰ is —C₁₋₆alkyl; R²¹ is H; and R²² and R²³ are independently selected from —C₁₋₆alkyl, —(CH₂)₂OCH₃, and —C₃₋₇cycloalkyl; or R²² and R²³ are taken together to form a saturated —C₃₋₅heterocycle; R⁴ is selected from H, —OH, —C₁₋₆alkyl, —CH₂OC(O)CH(R³⁶)NH₂, —CH₂OP(O)(OH)₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and benzyl; a is 0; b is 0 or b is 1 and R⁶ is halo; and the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups.

In still another embodiment, X is selected from pyrazole, triazole, benzotriazole, oxazole, isoxazole, and pyrimidine; R³ is selected from H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²¹ is H; R²² and R² are taken together to form a saturated —C₃₋₅heterocycle; R⁴ is selected from H and —OH; a is 0; b is 0 or b is 1 and R⁶ is halo; and the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups.

A particular group of compounds of formula I are those disclosed in U.S. Provisional Application No. 61/443,827, filed on Feb. 17, 2011. This group includes compounds of formula II:

where: R¹ is selected from —OR⁷ and —NR⁸R⁹; R⁷ is selected from H; —C₁₋₆alkyl; —C₁₋₃alkylene-C₆₋₁₀aryl; —C₁₋₃alkylene-C₁₋₉heteroaryl; —C₃₋₇cycloalkyl; —[(CH₂)₂O]₁₋₃CH₃; —C₁₋₆alkylene-OC(O)R¹⁰; —CH₂-pyridine; —CH₂-pyrrolidine; —C₀₋₆alkylenemorpholine; —C₁₋₆alkylene-SO₂—C₁₋₆alkyl;

where R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹²R¹³, and —CH(NH₂)CH₂COOCH₃; and R¹² and R¹³ are independently selected from H, —C₁₋₆alkyl, and benzyl, or R¹² and R¹³ are taken together as —(CH₂)₃₋₆—; R⁸ is selected from H; —OH; —OC(O)R¹⁴; —CH₂COOH; —O-benzyl; pyridyl; and —OC(S)NR¹⁵R¹⁶; where R¹⁴ is selected from H, —C₁₋₆alkyl, —C₆₋₁₀aryl, —OCH₂—C₆₋₁₀aryl, —CH₂O—C₆₋₁₀aryl, and —NR¹⁵R¹⁶; and R¹⁵ and R¹⁶ are independently selected from H and —C₁₋₄alkyl; R⁹ is selected from H; —C₁₋₄alkyl; and —C(O)R¹⁷; where R¹⁷ is selected from H; —C₁₋₆alkyl; —C₃₋₇cycloalkyl; —C₆₋₁₀aryl; and —C₁₋₉heteroaryl; R² is H or —CH₃; Z is selected from —CH— and —N—; X is a —C₁₋₉heteroaryl or a partially unsaturated —C₃₋₅heterocycle; R³ is absent or is selected from H; halo; —C₀₋₅alkylene-OH; —NH₂; —C₁₋₆alkyl; —CF₃; —C₃₋₇cycloalkyl; —C₀₋₁alkylene-O—C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-C(O)OR²¹; —C(O)NR²²R²³; —NHC(O)R²⁴; phenyl optionally substituted with one group selected from halo, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl; napthyl; pyridine; pyrazine; pyrazole optionally substituted with methyl; thiophene optionally substituted with methyl; and furan; and R³, when present, is attached to a carbon atom; R²⁰ is selected from H and —C₁₋₆alkyl; R²¹ is selected from H; —C₁₋₄alkyl; —C₁₋₃alkylene-C₆₋₁₀aryl; —C₁₋₃alkylene-C₁₋₉heteroaryl; —C₃₋₇cycloalkyl; —[(CH₂)₂O]₁₋₃CH₃; —C₄alkylene-OC(O)R²⁵; —CH₂-pyridine; —CH₂-pyrrolidine; —C₀₋₆alkylenemorpholine; —C₁₋₆alkylene-SO₂—C₁₋₆alkyl;

where R²⁵ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR²⁷R²⁸, and —CH(NH₂)CH₂COOCH₃; and R²⁷ and R²⁸ are independently selected from H, —C₁₋₆alkyl, and benzyl, or R²⁷ and R²⁸ are taken together as —(CH₂)₃₋₆—; R²² and R²³ are independently selected from H; —C₁₋₆alkyl; —CH₂COOH; —(CH₂)₂OH; —(CH₂)₂OCH₃; —(CH₂)₂SO₂NH₂; —(CH₂)₂N(CH₃)₂; —C₃₋₇cycloalkyl; and —(CH₂)₂-imidazole; or R²² and R²³ are taken together to form a saturated or partially unsaturated —C₃₋₅heterocycle optionally substituted with —OH, —COOH, or —CONH₂; and optionally containing an oxygen atom in the ring; R²⁴ is selected from —C₁₋₆alkyl; —C₀₋₁alkylene-O—C₁₋₆alkyl; phenyl optionally substituted with —OCH₃; and —C₁₋₉heteroaryl; R⁴ is absent or is selected from H; —C₁₋₆alkyl; and phenyl or benzyl substituted with one or more groups selected from halo, —COOH, —OCH₃, —OCF₃, and —SCF₃; and R⁴, when present, is attached to a carbon or nitrogen atom; a is 0 or 1; R⁵ is halo, —CH₃, or —CF₃; and b is 0 or 1; R⁶ is halo; or a pharmaceutically acceptable salt thereof.

In addition, particular compounds of formula I that are of interest include those set forth in the Examples below, as well as pharmaceutically acceptable salts thereof.

General Synthetic Procedures

Compounds of the invention can be prepared from readily available starting materials using the following general methods, the procedures set forth in the Examples, or by using other methods, reagents, and starting materials that are known to those of ordinary skill in the art. Although the following procedures may illustrate a particular embodiment of the invention, it is understood that other embodiments of the invention can be similarly prepared using the same or similar methods or by using other methods, reagents and starting materials known to those of ordinary skill in the art. It will also be appreciated that where typical or preferred process conditions (for example, reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions can also be used unless otherwise stated. In some instances, reactions were conducted at room temperature and no actual temperature measurement was taken. It is understood that room temperature can be taken to mean a temperature within the range commonly associated with the ambient temperature in a laboratory environment, and will typically be in the range of about 18° C. to about 30° C. In other instances, reactions were conducted at room temperature and the temperature was actually measured and recorded. While optimum reaction conditions will typically vary depending on various reaction parameters such as the particular reactants, solvents and quantities used, those of ordinary skill in the art can readily determine suitable reaction conditions using routine optimization procedures.

Additionally, as will be apparent to those skilled in the art, conventional protecting groups may be necessary or desired to prevent certain functional groups from undergoing undesired reactions. The choice of a suitable protecting group for a particular functional group as well as suitable conditions and reagents for protection and deprotection of such functional groups are well-known in the art. Protecting groups other than those illustrated in the procedures described herein may be used, if desired. For example, numerous protecting groups, and their introduction and removal, are described in T. W. Greene and G. M. Wuts, Protecting Groups in Organic Synthesis, Fourth Edition, Wiley, New York, 2006, and references cited therein.

Carboxy-protecting groups are suitable for preventing undesired reactions at a carboxy group, and examples include, but are not limited to, methyl, ethyl, t-butyl, benzyl (Bn), p-methoxybenzyl (PMB), 9-fluorenylmethyl (Fm), trimethylsilyl (TMS), t-butyldimethylsilyl (TBDMS), diphenylmethyl (benzhydryl, DPM) and the like. Amino-protecting groups are suitable for preventing undesired reactions at an amino group, and examples include, but are not limited to, t-butoxycarbonyl (BOC), trityl (Tr), benzyloxycarbonyl (Cbz), 9-fluorenylmethoxycarbonyl (Fmoc), formyl, trimethylsilyl (TMS), t-butyldimethylsilyl (TBDMS), and the like. Hydroxyl-protecting groups are suitable for preventing undesired reactions at a hydroxyl group, and examples include, but are not limited to C₁₋₆alkyls, silyl groups including triC₁₋₆alkylsilyl groups, such as trimethylsilyl (TMS), triethylsilyl (TES), and tert-butyldimethylsilyl (TBDMS); esters (acyl groups) including C₁₋₆alkanoyl groups, such as formyl, acetyl, and pivaloyl, and aromatic acyl groups such as benzoyl; arylmethyl groups such as benzyl (Bn), p-methoxybenzyl (PMB), 9-fluorenylmethyl (Fm), and diphenylmethyl (benzhydryl, DPM); and the like.

Standard deprotection techniques and reagents are used to remove the protecting groups, and may vary depending upon which group is used. For example, sodium or lithium hydroxide is commonly used when the carboxy-protecting group is methyl, an acid such as TFA or HCl is commonly used when the carboxy-protecting group is ethyl or t-butyl, and H₂/Pd/C may be used when the carboxy-protecting group is benzyl. A BOC amino-protecting group can be removed using an acidic reagent such as TFA in DCM or HCl in 1,4-dioxane, while a Cbz amino-protecting group can be removed by employing catalytic hydrogenation conditions such as H₂ (1 atm) and 10% Pd/C in an alcoholic solvent (“H₂/Pd/C”). H₂/Pd/C is commonly used when the hydroxyl-protecting group is benzyl, while NaOH is commonly used when the hydroxyl-protecting group is an acyl group.

Suitable bases for use in these schemes include, by way of illustration and not limitation, potassium carbonate, calcium carbonate, sodium carbonate, triethylamine, pyridine, 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU), N,N-diisopropylethylamine (DIPEA), 4-methylmorpholine, sodium hydroxide, potassium hydroxide, potassium t-butoxide, and metal hydrides.

Suitable inert diluents or solvents for use in these schemes include, by way of illustration and not limitation, tetrahydrofuran (THF), acetonitrile (MeCN), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), toluene, dichloromethane (DCM), chloroform (CHCl₃), carbon tetrachloride (CCl₄), 1,4-dioxane, methanol, ethanol, water, and the like.

Suitable carboxylic acid/amine coupling reagents include benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP), benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (HATU), (2-(6-chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium hexafluorophosphate) (HCTU), 1,3-dicyclohexylcarbodiimide (DCC), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDCI), carbonyldiimidazole (CDI), 1-hydroxybenzotriazole (HOBt), and the like. Coupling reactions are conducted in an inert diluent in the presence of a base such as DIPEA, and are performed under conventional amide bond-forming conditions.

All reactions are typically conducted at a temperature within the range of about −78 C. to 100° C., for example at room temperature. Reactions may be monitored by use of thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and/or LCMS until completion. Reactions may be complete in minutes, or may take hours, typically from 1-2 hours and up to 48 hours. Upon completion, the resulting mixture or reaction product may be further treated in order to obtain the desired product. For example, the resulting mixture or reaction product may be subjected to one or more of the following procedures: concentrating or partitioning (for example, between EtOAc and water or between 5% THF in EtOAc and IM phosphoric acid); extraction (for example, with EtOAc, CHCl₃, DCM, chloroform); washing (for example, with saturated aqueous NaCl, saturated aqueous NaHCO₃, Na₂CO₃ (5%), CHCl₃ or 1M NaOH); drying (for example, over MgSO₄, over Na₂SO₄, or in vacuo); filtering; crystallizing (for example, from EtOAc and hexanes); being concentrated (for example, in vacuo); and/or purification (e.g., silica gel chromatography, flash chromatography, preparative HPLC, reverse phase-HPLC, or crystallization).

Compounds of formula I, as well as their salts, can be prepared as shown in Scheme I:

The process comprises the step of coupling compound 1 with compound 2, where R¹, R^(2a), R^(2b), R³-R⁶, X, Z, a, and b are as defined for formula I, and P¹ is H or a suitable amino-protecting group, examples of which include, t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl. When P¹ is an amino protecting group, the process further comprises deprotecting the compound of formula 1, before or in situ with the coupling step.

In instances where R¹ is a group such as —OCH₃ or —OCH₂CH₃, the coupling step may be followed by a deprotection step to provide a compound of formula I where R¹ is a group such as —OH. Thus, one method of preparing compounds of the invention involves coupling compounds 1 and 2, with an optional deprotection step to form a compound of formula I or a pharmaceutically acceptable salt thereof.

Methods of preparing compound 1 are described in the Examples. Compound 2 is generally commercially available or can be prepared using procedures that are known in the art.

Compounds of formula I, as well as their salts, can also be prepared as shown in Scheme II:

In this method, compound 3 is coupled with compound 4, the amine is deprotected and the intermediate is then coupled to 5 to form a compound of formula I or a pharmaceutically acceptable salt thereof. Methods of preparing compound 4 are described in the Examples. Compounds 3 and 5 are generally commercially available or can be prepared using procedures that are known in the art.

Compounds of formula I, as well as their salts, can also be prepared as shown in Scheme III:

In the first step, compound 1 is coupled with compound 6 and compound 6 is coupled to compound 7, where Y and Z react in situ to form the R³ moiety. For example, when R³ is —C(O)NR²²R²³, Y is —COOH and Z is HNR²²R²³. Alternately, compound 6 is first coupled to compound 7, and the resulting compound is then coupled with compound 1. As with Scheme I, in instances where R¹ is a group such as —OCH₃ or —OCH₂CH₃, the coupling step may be followed by a deprotection step to provide a compound of formula I where R¹ is a group such as —OH. Thus, one method of preparing compounds of the invention involves coupling compounds 1, 2 and 3, with an optional deprotection step to form a compound of formula I or a pharmaceutically acceptable salt thereof. Compounds 6 and 7 are generally commercially available or can be prepared using procedures that are known in the art.

Compounds of formula I, as well as their salts, can also be prepared as shown in Scheme IV:

Again, this is a standard coupling reaction between a compound of formula I, where R¹ is —OH and compound 8, to yield a compound of formula I, where R¹ is —NR⁸R⁹.

Certain intermediates described herein are believed to be novel and accordingly, such compounds are provided as further aspects of the invention including, for example, the compounds of formula 1, or a salt thereof:

where P¹ is H or an amino-protecting group selected from t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; and R¹, R^(2a), R^(2b), R⁵, R⁶, Z, a and b are as defined for formula I. In one specific embodiment Z is —CH— and in another specific embodiment Z is —N—. These embodiments can be depicted as formulas 1a and 1b, respectively:

Another intermediate of the invention has formula 9 or a salt thereof:

where R^(1P) is selected from —O—P³, —NHP², and —NH(O—P⁴); where P² is an amino-protecting group selected from t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; P³ is a carboxy-protecting group selected from methyl, ethyl, t-butyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, trimethylsilyl, t-butyldimethylsilyl, and diphenylmethyl; P⁴ is a hydroxyl-protecting group selected from —C₁₋₆alkyl, triC₁₋₆alkylsilyl, —C₁₋₆alkanoyl, benzoyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, and diphenylmethyl; and R^(2a), R^(2b), R³, R⁴, R⁵, R⁶, a, b, Z, and X are as defined for formula I. Another intermediate of the invention has formula 10 or a salt thereof:

where R^(3P) is selected from —C₀₋₅alkylene-O—P⁴, —C₀₋₁alkylene-COO—P³, and phenyl substituted with —O—P⁴; P³ is a carboxy-protecting group selected from methyl, ethyl, t-butyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, trimethylsilyl, t-butyldimethylsilyl, and diphenylmethyl; P⁴ is a hydroxyl-protecting group selected from —C₁₋₆alkyl, triC₁₋₆alkylsilyl, —C₁₋₆alkanoyl, benzoyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, and diphenylmethyl; and R¹, R^(2a), R^(2b), R⁴, R⁵, R⁶, a, b, Z, and X are as defined for formula I. Still another intermediate of the invention has formula 11 or a salt thereof:

where R^(4P) is selected from —O—P⁴; —C₁₋₂alkylene-COO—P³; and phenyl or benzyl substituted with —COO—P³; P³ is a carboxy-protecting group selected from methyl, ethyl, t-butyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, trimethylsilyl, t-butyldimethylsilyl, and diphenylmethyl; P⁴ is a hydroxyl-protecting group selected from —C₁₋₆alkyl, triC₁₋₆alkylsilyl, —C₁₋₆alkanoyl, benzoyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, and diphenylmethyl; and R¹, R^(2a), R^(2b), R³, R⁵, R⁶, a, b, Z, and X are as defined for formula I. Yet another intermediate of the invention has formula 12 or a salt thereof:

where R^(3P) is selected from —C₀₋₅alkylene-O—P⁴, —C₀₋₁alkylene-COO—P³, and phenyl substituted with —O—P⁴; R^(4P) is selected from —O—P⁴; —C₁₋₂alkylene-COO—P³; and phenyl or benzyl substituted with —COO—P³; P³ is a carboxy-protecting group selected from methyl, ethyl, t-butyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, trimethylsilyl, t-butyldimethylsilyl, and diphenylmethyl; P⁴ is a hydroxyl-protecting group selected from —C₁₋₆alkyl, triC₁₋₆alkylsilyl, —C₁₋₆alkanoyl, benzoyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, and diphenylmethyl; and R¹, R^(2a), R^(2b), R⁵, R⁶, a, b, Z, and X are as defined for formula I. Thus, another method of preparing compounds of the invention involves deprotecting a compound of formula 1, 9, 10, 11, 12, or a salt thereof.

Further details regarding specific reaction conditions and other procedures for preparing representative compounds of the invention or intermediates thereof are described in the Examples set forth below.

Utility

Compounds of the invention possess neprilysin (NEP) inhibition activity, that is, the compounds are able to inhibit enzyme-catalytic activity. In another embodiment, the compounds do not exhibit significant inhibitory activity of the angiotensin-converting enzyme. One measure of the ability of a compound to inhibit NEP activity is the inhibition constant (pK_(i)). The pK_(i) value is the negative logarithm to base 10 of the dissociation constant (K_(i)), which is typically reported in molar units. Compounds of the invention of particular interest are those having a pK_(i) at NEP greater than or equal to 6.0, particularly those having a pK_(i) greater than or equal to 7.0, and even more particularly those having a pK_(i) greater than or equal to 8.0. In one embodiment, compounds of interest have a pK_(i) in the range of 6.0-6.9; in another embodiment, compounds of interest have a pK_(i) in the range of 7.0-7.9; in yet another embodiment, compounds of interest have a pK_(i) in the range of 8.0-8.9; and in still another embodiment, compounds of interest have a pK_(i) in the range of greater than or equal to 9.0. Such values can be determined by techniques that are well known in the art, as well as in the assays described herein.

Another measure of the ability of a compound to inhibit NEP activity is the apparent inhibition constant (IC₅₀), which is the molar concentration of compound that results in half-maximal inhibition of substrate conversion by the NEP enzyme. The pIC₅₀ value is the negative logarithm to base 10 of the IC₅₀. Compounds of the invention that are of particular interest, include those that exhibit a pIC₅₀ for NEP greater than or equal to about 5.0. Compounds of interest also include those having a pIC₅₀ for NEP ≧about 6.0 or a pIC₅₀ for NEP ≧about 7.0. In another embodiment, compounds of interest have a pIC₅₀ for NEP within the range of about 7.0-10.0; and in another embodiment, within the range of about 8.0-11.0, such as within the range of about 8.0-10.0.

It is noted that in some cases, compounds of the invention may possess weak NEP inhibition activity. In such cases, those of skill in the art will recognize that these compounds still have utility as research tools.

Exemplary assays to determine properties of compounds of the invention, such as the NEP inhibiting activity, are described in the Examples and include by way of illustration and not limitation, assays that measure NEP inhibition (described in Assay 1). Useful secondary assays include assays to measure ACE inhibition (also described in Assay 1) and aminopeptidase P (APP) inhibition (described in Sulpizio et al. (2005) JPET 315:1306-1313). A pharmacodynamic assay to assess the in vivo inhibitory potencies for ACE and NEP in anesthetized rats is described in Assay 2 (see also Seymour et al. (1985) Hypertension 7(Suppl I):I-35-1-42 and Wigle et al. (1992) Can. J. Physiol. Pharmacol. 70:1525-1528), where ACE inhibition is measured as the percent inhibition of the angiotensin I pressor response and NEP inhibition is measured as increased urinary cyclic guanosine 3′,5′-monophosphate (cGMP) output.

There are many in vivo assays that can be used to ascertain further utilities of the compounds of the invention. The conscious spontaneously hypertensive rat (SHR) model is a renin dependent hypertension model, and is described in Assay 3. See also Intengan et al. (1999) Circulation 100(22):2267-2275 and Badyal et al. (2003) Indian Journal of Pharmacology 35:349-362. The conscious desoxycorticosterone acetate-salt (DOCA-salt) rat model is a volume dependent hypertension model that is useful for measuring NEP activity, and is described in Assay 4. See also Trapani et al. (1989) J. Cardiovasc. Pharmacol. 14:419-424, Intengan et al. (1999) Hypertension 34(4):907-913, and Badyal et al. (2003) supra). The DOCA-salt model is particularly useful for evaluating the ability of a test compound to reduce blood pressure as well as to measure a test compound's ability to prevent or delay a rise in blood pressure. The Dahl salt-sensive (DSS) hypertensive rat model is a model of hypertension that is sensitive to dietary salt (NaCl), and is described in Assay 5. See also Rapp (1982) Hypertension 4:753-763. The rat monocrotaline model of pulmonary arterial hypertension described, for example, in Kato et al. (2008) J. Cardiovasc. Pharmacol. 51(1):18-23, is a reliable predictor of clinical efficacy for the treatment of pulmonary arterial hypertension. Heart failure animal models include the DSS rat model for heart failure and the aorto-caval fistula model (AV shunt), the latter of which is described, for example, in Norling et al. (1996) J. Amer. Soc. Nephrol. 7:1038-1044. Other animal models, such as the hot plate, tail-flick and formalin tests, can be used to measure the analgesic properties of compounds of the invention, as well as the spinal nerve ligation (SNL) model of neuropathic pain. See, for example, Malmberg et al. (1999) Current Protocols in Neuroscience 8.9.1-8.9.15.

Compounds of the invention are expected to inhibit the NEP enzyme in any of the assays listed above, or assays of a similar nature. Thus, the aforementioned assays are useful in determining the therapeutic utility of compounds of the invention, for example, their utility as antihypertensive agents or antidiarrheal agents. Other properties and utilities of compounds of the invention can be demonstrated using other in vitro and in vivo assays well-known to those skilled in the art. Compounds of formula I may be active drugs as well as prodrugs. Thus, when discussing the activity of compounds of the invention, it is understood that any such prodrugs may not exhibit the expected activity in an assay, but are expected to exhibit the desired activity once metabolized.

Compounds of the invention are expected to be useful for the treatment and/or prevention of medical conditions responsive to NEP inhibition. Thus it is expected that patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme or by increasing the levels of its peptide substrates, can be treated by administering a therapeutically effective amount of a compound of the invention. For example, by inhibiting NEP, the compounds are expected to potentiate the biological effects of endogenous peptides that are metabolized by NEP, such as the natriuretic peptides, bombesin, bradykinins, calcitonin, endothelins, enkephalins, neurotensin, substance P and vasoactive intestinal peptide. Thus, these compounds are expected to have other physiological actions, for example, on the renal, central nervous, reproductive and gastrointestinal systems.

In one embodiment of the invention, patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme, are treated by administering a compound of the invention that is in its active form, i.e., a compound of formula I where R¹ is selected from —OR⁷ and —NR⁸R⁹, R⁷ is H, R⁸ is H or —OH, R⁹ is H, and R^(2a), R^(2b), R³-R⁶, a, b, Z, and X are as defined for formula I.

In another embodiment, patients are treated by administering a compound that is metabolized in vitro to form a compound of formula I where R¹ is selected from —OR⁷ and —NR⁸R⁹, R⁷ is H, R⁸ is H or —OH, R⁹ is H, and R^(2a), R^(2b), R³-R⁶, a, b, Z, and X are as defined for formula I. In an exemplary embodiment, patients are treated by administering a compound that is metabolized in vitro to form a compound of formula VI where R¹ is —OR⁷ and R⁷ is H.

In another embodiment, patients are treated by administering a compound of the invention that is in its prodrug form at the R¹ group, i.e., a compound of formula I where:

R¹ is —OR⁷; and R⁷ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹ is —NR⁸R⁹; R⁸ is selected from —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is H; or

R¹ is —NR⁸R⁹; R⁸ is selected from —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is —C₁₋₆alkyl or —C(O)R¹⁷;

R¹ is —NR⁸R⁹; R⁸ is selected from H or —OH; and R⁹ is selected from —C₁₋₆alkyl, and —C(O)R¹⁷;

R¹ is —OR⁷ and R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—; or

R¹ is —NR⁸R⁹ and R^(2a) is taken together with R⁸ to form —CH₂O—C(O)—;

and R^(b), R¹⁰, R¹²-R¹⁷, R³¹, R³², R³-R⁶, a, b, Z, and X are as defined for formula I. In an exemplary embodiment, patients are treated by administering a compound of the invention that is in its prodrug form at the R¹ group and has formula III, IV, V, or VI.

Cardiovascular Diseases

By potentiating the effects of vasoactive peptides like the natriuretic peptides and bradykinin, compounds of the invention are expected to find utility in treating and/or preventing medical conditions such as cardiovascular diseases. See, for example, Roques et al. (1993) Pharmacol. Rev. 45:87-146 and Dempsey et al. (2009) Amer. J. of Pathology 174(3):782-796. Cardiovascular diseases of particular interest include hypertension and heart failure. Hypertension includes, by way of illustration and not limitation: primary hypertension, which is also referred to as essential hypertension or idiopathic hypertension; secondary hypertension; hypertension with accompanying renal disease; severe hypertension with or without accompanying renal disease; pulmonary hypertension, including pulmonary arterial hypertension; and resistant hypertension. Heart failure includes, by way of illustration and not limitation: congestive heart failure; acute heart failure; chronic heart failure, for example with reduced left ventricular ejection fraction (also referred to as systolic heart failure) or with preserved left ventricular ejection fraction (also referred to as diastolic heart failure); and acute and chronic decompensated heart failure, with or without accompanying renal disease. Thus, one embodiment of the invention relates to a method for treating hypertension, particularly primary hypertension or pulmonary arterial hypertension, comprising administering to a patient a therapeutically effective amount of a compound of the invention.

For treatment of primary hypertension, the therapeutically effective amount is typically the amount that is sufficient to lower the patient's blood pressure. This would include both mild-to-moderate hypertension and severe hypertension. When used to treat hypertension, the compound may be administered in combination with other therapeutic agents such as aldosterone antagonists, aldosterone synthase inhibitors, angiotensin-converting enzyme inhibitors and dual-acting angiotensin-converting enzyme/neprilysin inhibitors, angiotensin-converting enzyme 2 (ACE2) activators and stimulators, angiotensin-II vaccines, anti-diabetic agents, anti-lipid agents, anti-thrombotic agents, AT₁ receptor antagonists and dual-acting AT₁ receptor antagonist/neprilysin inhibitors, β₁-adrenergic receptor antagonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, calcium channel blockers, diuretics, endothelin receptor antagonists, endothelin converting enzyme inhibitors, neprilysin inhibitors, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, nitric oxide donors, non-steroidal anti-inflammatory agents, phosphodiesterase inhibitors (specifically PDE-V inhibitors), prostaglandin receptor agonists, renin inhibitors, soluble guanylate cyclase stimulators and activators, and combinations thereof. In one particular embodiment of the invention, a compound of the invention is combined with an AT₁ receptor antagonist, a calcium channel blocker, a diuretic, or a combination thereof, and used to treat primary hypertension. In another particular embodiment of the invention, a compound of the invention is combined with an AT₁ receptor antagonist, and used to treat hypertension with accompanying renal disease. When used to treat resistant hypertension, the compound may be administered in combination with other therapeutic agents such as aldosterone synthase inhibitors.

For treatment of pulmonary arterial hypertension, the therapeutically effective amount is typically the amount that is sufficient to lower the pulmonary vascular resistance. Other goals of therapy are to improve a patient's exercise capacity. For example, in a clinical setting, the therapeutically effective amount can be the amount that improves a patient's ability to walk comfortably for a period of 6 minutes (covering a distance of approximately 20-40 meters). When used to treat pulmonary arterial hypertension the compound may be administered in combination with other therapeutic agents such as α-adrenergic receptor antagonists, β-adrenergic receptor antagonists, β₂-adrenergic receptor agonists, angiotensin-converting enzyme inhibitors, anticoagulants, calcium channel blockers, diuretics, endothelin receptor antagonists, PDE-V inhibitors, prostaglandin analogs, selective serotonin reuptake inhibitors, and combinations thereof. In one particular embodiment of the invention, a compound of the invention is combined with a PDE-V inhibitor or a selective serotonin reuptake inhibitor and used to treat pulmonary arterial hypertension.

Another embodiment of the invention relates to a method for treating heart failure, in particular congestive heart failure (including both systolic and diastolic congestive heart failure), comprising administering to a patient a therapeutically effective amount of a compound of the invention. Typically, the therapeutically effective amount is the amount that is sufficient to lower blood pressure and/or improve renal functions. In a clinical setting, the therapeutically effective amount can be the amount that is sufficient to improve cardiac hemodynamics, like for instance reduction in wedge pressure, right atrial pressure, filling pressure, and vascular resistance. In one embodiment, the compound is administered as an intravenous dosage form. When used to treat heart failure, the compound may be administered in combination with other therapeutic agents such as adenosine receptor antagonists, advanced glycation end product breakers, aldosterone antagonists, AT₁ receptor antagonists, β₁-adrenergic receptor antagonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, chymase inhibitors, digoxin, diuretics, endothelin converting enzyme (ECE) inhibitors, endothelin receptor antagonists, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, nitric oxide donors, prostaglandin analogs, PDE-V inhibitors, soluble guanylate cyclase activators and stimulators, and vasopressin receptor antagonists. In one particular embodiment of the invention, a compound of the invention is combined with an aldosterone antagonist, a β₁-adrenergic receptor antagonist, an AT₁ receptor antagonist, or a diuretic, and used to treat congestive heart failure.

Diarrhea

As NEP inhibitors, compounds of the invention are expected to inhibit the degradation of endogenous enkephalins and thus such compounds may also find utility for the treatment of diarrhea, including infectious and secretory/watery diarrhea. See, for example, Baumer et al. (1992) Gut 33:753-758; Farthing (2006) Digestive Diseases 24:47-58; and Marcais-Collado (1987) Eur. J. Pharmacol. 144(2):125-132. When used to treat diarrhea, compounds of the invention may be combined with one or more additional antidiarrheal agents.

Renal Diseases

By potentiating the effects of vasoactive peptides like the natriuretic peptides and bradykinin, compounds of the invention are expected to enhance renal function (see Chen et al. (1999) Circulation 100:2443-2448; Lipkin et al. (1997) Kidney Int. 52:792-801; and Dussaule et al. (1993) Clin. Sci. 84:31-39) and find utility in treating and/or preventing renal diseases. Renal diseases of particular interest include diabetic nephropathy, chronic kidney disease, proteinuria, and particularly acute kidney injury or acute renal failure (see Sharkovska et al. (2011) Clin. Lab. 57:507-515 and Newaz et al. (2010) Renal Failure 32:384-390). When used to treat renal disease, the compound may be administered in combination with other therapeutic agents such as angiotensin-converting enzyme inhibitors, AT₁ receptor antagonists, and diuretics.

Preventative Therapy

By potentiating the effects of the natriuretic peptides, compounds of the invention are also expected to be useful in preventative therapy, due to the antihypertrophic and antifibrotic effects of the natriuretic peptides (see Potter et al. (2009) Handbook of Experimental Pharmacology 191:341-366), for example in preventing the progression of cardiac insufficiency after myocardial infarction, preventing arterial restenosis after angioplasty, preventing thickening of blood vessel walls after vascular operations, preventing atherosclerosis, and preventing diabetic angiopathy.

Glaucoma

By potentiating the effects of the natriuretic peptides, compounds of the invention are expected to be useful to treat glaucoma. See, for example, Diestelhorst et al. (1989) International Ophthalmology 12:99-101. When used to treat glaucoma, compounds of the invention may be combined with one or more additional antiglaucoma agents.

Pain Relief

As NEP inhibitors, compounds of the invention are expected to inhibit the degradation of endogenous enkephalins and thus such compounds may also find utility as analgesics. See, for example, Roques et al. (1980) Nature 288:286-288 and Thanawala et al. (2008) Current Drug Targets 9:887-894. When used to treat pain, the compounds of the invention may be combined with one or more additional antinociceptive drugs such as aminopeptidase N or dipeptidyl peptidase III inhibitors, non-steroidal anti-inflammatory agents, monoamine reuptake inhibitors, muscle relaxants, NMDA receptor antagonists, opioid receptor agonists, 5-HT_(1D) serotonin receptor agonists, and tricyclic antidepressants.

Other Utilities

Due to their NEP inhibition properties, compounds of the invention are also expected to be useful as antitussive agents, as well as find utility in the treatment of portal hypertension associated with liver cirrhosis (see Sansoe et al. (2005) J. Hepatol. 43:791-798), cancer (see Vesely (2005) J. Investigative Med. 53:360-365), depression (see Noble et al. (2007) Exp. Opin. Ther. Targets 11:145-159), menstrual disorders, preterm labor, pre-eclampsia, endometriosis, reproductive disorders (for example, male and female infertility, polycystic ovarian syndrome, implantation failure), and male and female sexual dysfunction, including male erectile dysfunction and female sexual arousal disorder. More specifically, the compounds of the invention are expected to be useful in treating female sexual dysfunction (see Pryde et al. (2006) J. Med. Chem. 49:4409-4424), which is often defined as a female patient's difficulty or inability to find satisfaction in sexual expression. This covers a variety of diverse female sexual disorders including, by way of illustration and not limitation, hypoactive sexual desire disorder, sexual arousal disorder, orgasmic disorder and sexual pain disorder. When used to treat such disorders, especially female sexual dysfunction, compounds of the invention may be combined with one or more of the following secondary agents: PDE-V inhibitors, dopamine agonists, estrogen receptor agonists and/or antagonists, androgens, and estrogens. Due to their NEP inhibition properties, compounds of the invention are also expected to have anti-inflammatory properties, and are expected to have utility as such, particularly when used in combination with statins.

Recent studies suggest that NEP plays a role in regulating nerve function in insulin-deficient diabetes and diet induced obesity. Coppey et al. (2011) Neuropharmacology 60:259-266. Therefore, due to their NEP inhibition properties, compounds of the invention are also expected to be useful in providing protection from nerve impairment caused by diabetes or diet induced obesity.

The amount of the compound of the invention administered per dose or the total amount administered per day may be predetermined or it may be determined on an individual patient basis by taking into consideration numerous factors, including the nature and severity of the patient's condition, the condition being treated, the age, weight, and general health of the patient, the tolerance of the patient to the active agent, the route of administration, pharmacological considerations such as the activity, efficacy, pharmacokinetics and toxicology profiles of the compound and any secondary agents being administered, and the like. Treatment of a patient suffering from a disease or medical condition (such as hypertension) can begin with a predetermined dosage or a dosage determined by the treating physician, and will continue for a period of time necessary to prevent, ameliorate, suppress, or alleviate the symptoms of the disease or medical condition. Patients undergoing such treatment will typically be monitored on a routine basis to determine the effectiveness of therapy. For example, in treating hypertension, blood pressure measurements may be used to determine the effectiveness of treatment. Similar indicators for other diseases and conditions described herein, are well known and are readily available to the treating physician. Continuous monitoring by the physician will insure that the optimal amount of the compound of the invention will be administered at any given time, as well as facilitating the determination of the duration of treatment. This is of particular value when secondary agents are also being administered, as their selection, dosage, and duration of therapy may also require adjustment. In this way, the treatment regimen and dosing schedule can be adjusted over the course of therapy so that the lowest amount of active agent that exhibits the desired effectiveness is administered and, further, that administration is continued only so long as is necessary to successfully treat the disease or medical condition.

Research Tools

Since compounds of the invention possess NEP enzyme inhibition activity, such compounds are also useful as research tools for investigating or studying biological systems or samples having a NEP enzyme, for example to study diseases where the NEP enzyme or its peptide substrates plays a role. Any suitable biological system or sample having a NEP enzyme may be employed in such studies which may be conducted either in vitro or in vivo. Representative biological systems or samples suitable for such studies include, but are not limited to, cells, cellular extracts, plasma membranes, tissue samples, isolated organs, mammals (such as mice, rats, guinea pigs, rabbits, dogs, pigs, humans, and so forth), and the like, with mammals being of particular interest. In one particular embodiment of the invention, NEP enzyme activity in a mammal is inhibited by administering a NEP-inhibiting amount of a compound of the invention. Compounds of the invention can also be used as research tools by conducting biological assays using such compounds.

When used as a research tool, a biological system or sample comprising a NEP enzyme is typically contacted with a NEP enzyme-inhibiting amount of a compound of the invention. After the biological system or sample is exposed to the compound, the effects of inhibiting the NEP enzyme are determined using conventional procedures and equipment, such as by measuring receptor binding in a binding assay or measuring ligand-mediated changes in a functional assay. Exposure encompasses contacting cells or tissue with the compound, administering the compound to a mammal, for example by i.p., p.o, i.v., s.c., or inhaled administration, and so forth. This determining step can involve measuring a response (a quantitative analysis) or can involve making an observation (a qualitative analysis). Measuring a response involves, for example, determining the effects of the compound on the biological system or sample using conventional procedures and equipment, such as enzyme activity assays and measuring enzyme substrate or product mediated changes in functional assays. The assay results can be used to determine the activity level as well as the amount of compound necessary to achieve the desired result, that is, a NEP enzyme-inhibiting amount. Typically, the determining step will involve determining the effects of inhibiting the NEP enzyme.

Additionally, compounds of the invention can be used as research tools for evaluating other chemical compounds, and thus are also useful in screening assays to discover, for example, new compounds having NEP-inhibiting activity. In this manner, a compound of the invention is used as a standard in an assay to allow comparison of the results obtained with a test compound and with compounds of the invention to identify those test compounds that have about equal or superior activity, if any. For example, pK_(i) data for a test compound or a group of test compounds is compared to the pK_(i) data for a compound of the invention to identify those test compounds that have the desired properties, for example, test compounds having a pK_(i) value about equal or superior to a compound of the invention, if any. This aspect of the invention includes, as separate embodiments, both the generation of comparison data (using the appropriate assays) and the analysis of test data to identify test compounds of interest. Thus, a test compound can be evaluated in a biological assay, by a method comprising the steps of: (a) conducting a biological assay with a test compound to provide a first assay value; (b) conducting the biological assay with a compound of the invention to provide a second assay value; wherein step (a) is conducted either before, after or concurrently with step (b); and (c) comparing the first assay value from step (a) with the second assay value from step (b). Exemplary biological assays include a NEP enzyme inhibition assay.

Pharmaceutical Compositions and Formulations

Compounds of the invention are typically administered to a patient in the form of a pharmaceutical composition or formulation. Such pharmaceutical compositions may be administered to the patient by any acceptable route of administration including, but not limited to, oral, rectal, vaginal, nasal, inhaled, topical (including transdermal), ocular, and parenteral modes of administration. Further, the compounds of the invention may be administered, for example orally, in multiple doses per day (for example, two, three, or four times daily), in a single daily dose or a single weekly dose. It will be understood that any form of the compounds of the invention, (that is, free base, free acid, pharmaceutically acceptable salt, solvate, etc.) that is suitable for the particular mode of administration can be used in the pharmaceutical compositions discussed herein.

Accordingly, in one embodiment, the invention relates to a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the invention. The compositions may contain other therapeutic and/or formulating agents if desired. When discussing compositions, the “compound of the invention” may also be referred to herein as the “active agent,” to distinguish it from other components of the formulation, such as the carrier. Thus, it is understood that the term “active agent” includes compounds of formula I as well as pharmaceutically acceptable salts, solvates and prodrugs of that compound.

The pharmaceutical compositions of the invention typically contain a therapeutically effective amount of a compound of the invention. Those skilled in the art will recognize, however, that a pharmaceutical composition may contain more than a therapeutically effective amount, such as in bulk compositions, or less than a therapeutically effective amount, that is, individual unit doses designed for multiple administration to achieve a therapeutically effective amount. Typically, the composition will contain from about 0.01-95 wt % of active agent, including, from about 0.01-30 wt %, such as from about 0.01-10 wt %, with the actual amount depending upon the formulation itself, the route of administration, the frequency of dosing, and so forth. In one embodiment, a composition suitable for an oral dosage form, for example, may contain about 5-70 wt %, or from about 10-60 wt % of active agent.

Any conventional carrier or excipient may be used in the pharmaceutical compositions of the invention. The choice of a particular carrier or excipient, or combinations of carriers or excipients, will depend on the mode of administration being used to treat a particular patient or type of medical condition or disease state. In this regard, the preparation of a suitable composition for a particular mode of administration is well within the scope of those skilled in the pharmaceutical arts. Additionally, carriers or excipients used in such compositions are commercially available. By way of further illustration, conventional formulation techniques are described in Remington: The Science and Practice of Pharmacy, 20^(th) Edition, Lippincott Williams & White, Baltimore, Md. (2000); and H. C. Ansel et al., Pharmaceutical Dosage Forms and Drug Delivery Systems, 7^(th) Edition, Lippincott Williams & White, Baltimore, Md. (1999).

Representative examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, the following: sugars, such as lactose, glucose and sucrose; starches, such as corn starch and potato starch; cellulose, such as microcrystalline cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients, such as cocoa butter and suppository waxes; oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; glycols, such as propylene glycol; polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; esters, such as ethyl oleate and ethyl laurate; agar; buffering agents, such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol; phosphate buffer solutions; compressed propellant gases, such as chlorofluorocarbons and hydrofluorocarbons; and other non-toxic compatible substances employed in pharmaceutical compositions.

Pharmaceutical compositions are typically prepared by thoroughly and intimately mixing or blending the active agent with a pharmaceutically acceptable carrier and one or more optional ingredients. The resulting uniformly blended mixture may then be shaped or loaded into tablets, capsules, pills, canisters, cartridges, dispensers and the like using conventional procedures and equipment.

In one embodiment, the pharmaceutical compositions are suitable for oral administration. Suitable compositions for oral administration may be in the form of capsules, tablets, pills, lozenges, cachets, dragees, powders, granules; solutions or suspensions in an aqueous or non-aqueous liquid; oil-in-water or water-in-oil liquid emulsions; elixirs or syrups; and the like; each containing a predetermined amount of the active agent.

When intended for oral administration in a solid dosage form (capsules, tablets, pills and the like), the composition will typically comprise the active agent and one or more pharmaceutically acceptable carriers, such as sodium citrate or dicalcium phosphate. Solid dosage forms may also comprise: fillers or extenders, such as starches, microcrystalline cellulose, lactose, sucrose, glucose, mannitol, and/or silicic acid; binders, such as carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; humectants, such as glycerol; disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and/or sodium carbonate; solution retarding agents, such as paraffin; absorption accelerators, such as quaternary ammonium compounds; wetting agents, such as cetyl alcohol and/or glycerol monostearate; absorbents, such as kaolin and/or bentonite clay; lubricants, such as talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and/or mixtures thereof; coloring agents; and buffering agents.

Release agents, wetting agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants may also be present in the pharmaceutical compositions. Exemplary coating agents for tablets, capsules, pills and like, include those used for enteric coatings, such as cellulose acetate phthalate, polyvinyl acetate phthalate, hydroxypropyl methylcellulose phthalate, methacrylic acid-methacrylic acid ester copolymers, cellulose acetate trimellitate, carboxymethyl ethyl cellulose, hydroxypropyl methyl cellulose acetate succinate, and the like. Examples of pharmaceutically acceptable antioxidants include: water-soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfate sodium sulfite and the like; oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, lecithin, propyl gallate, alpha-tocopherol, and the like; and metal-chelating agents, such as citric acid, ethylenediamine tetraacetic acid, sorbitol, tartaric acid, phosphoric acid, and the like.

Compositions may also be formulated to provide slow or controlled release of the active agent using, by way of example, hydroxypropyl methyl cellulose in varying proportions or other polymer matrices, liposomes and/or microspheres. In addition, the pharmaceutical compositions of the invention may contain opacifying agents and may be formulated so that they release the active agent only, or preferentially, in a certain portion of the gastrointestinal tract, optionally, in a delayed manner. Examples of embedding compositions which can be used include polymeric substances and waxes. The active agent can also be in micro-encapsulated form, optionally with one or more of the above-described excipients.

Suitable liquid dosage forms for oral administration include, by way of illustration, pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. Liquid dosage forms typically comprise the active agent and an inert diluent, such as, for example, water or other solvents, solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (for example, cottonseed, groundnut, corn, germ, olive, castor and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof. Suspensions may contain suspending agents such as, for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminium metahydroxide, bentonite, agar-agar and tragacanth, and mixtures thereof.

When intended for oral administration, the pharmaceutical compositions of the invention may be packaged in a unit dosage form. The term “unit dosage form” refers to a physically discrete unit suitable for dosing a patient, that is, each unit containing a predetermined quantity of the active agent calculated to produce the desired therapeutic effect either alone or in combination with one or more additional units. For example, such unit dosage forms may be capsules, tablets, pills, and the like.

In another embodiment, the compositions of the invention are suitable for inhaled administration, and will typically be in the form of an aerosol or a powder. Such compositions are generally administered using well-known delivery devices, such as a nebulizer, dry powder, or metered-dose inhaler. Nebulizer devices produce a stream of high velocity air that causes the composition to spray as a mist that is carried into a patient's respiratory tract. An exemplary nebulizer formulation comprises the active agent dissolved in a carrier to form a solution, or micronized and combined with a carrier to form a suspension of micronized particles of respirable size. Dry powder inhalers administer the active agent as a free-flowing powder that is dispersed in a patient's air-stream during inspiration. An exemplary dry powder formulation comprises the active agent dry-blended with an excipient such as lactose, starch, mannitol, dextrose, polylactic acid, polylactide-co-glycolide, and combinations thereof. Metered-dose inhalers discharge a measured amount of the active agent using compressed propellant gas. An exemplary metered-dose formulation comprises a solution or suspension of the active agent in a liquefied propellant, such as a chlorofluorocarbon or hydrofluoroalkane. Optional components of such formulations include co-solvents, such as ethanol or pentane, and surfactants, such as sorbitan trioleate, oleic acid, lecithin, glycerin, and sodium lauryl sulfate. Such compositions are typically prepared by adding chilled or pressurized hydrofluoroalkane to a suitable container containing the active agent, ethanol (if present) and the surfactant (if present). To prepare a suspension, the active agent is micronized and then combined with the propellant. Alternatively, a suspension formulation can be prepared by spray drying a coating of surfactant on micronized particles of the active agent. The formulation is then loaded into an aerosol canister, which forms a portion of the inhaler.

Compounds of the invention can also be administered parenterally (for example, by subcutaneous, intravenous, intramuscular, or intraperitoneal injection). For such administration, the active agent is provided in a sterile solution, suspension, or emulsion. Exemplary solvents for preparing such formulations include water, saline, low molecular weight alcohols such as propylene glycol, polyethylene glycol, oils, gelatin, fatty acid esters such as ethyl oleate, and the like. Parenteral formulations may also contain one or more anti-oxidants, solubilizers, stabilizers, preservatives, wetting agents, emulsifiers, and dispersing agents. Surfactants, additional stabilizing agents or pH-adjusting agents (acids, bases or buffers) and anti-oxidants are particularly useful to provide stability to the formulation, for example, to minimize or avoid hydrolysis of ester and amide linkages that may be present in the compound. These formulations may be rendered sterile by use of a sterile injectable medium, a sterilizing agent, filtration, irradiation, or heat. In one particular embodiment, the parenteral formulation comprises an aqueous cyclodextrin solution as the pharmaceutically acceptable carrier. Suitable cyclodextrins include cyclic molecules containing six or more α-D-glucopyranose units linked at the 1,4 positions by a linkages as in amylase, β-cyclodextrin or cycloheptaamylose. Exemplary cyclodextrins include cyclodextrin derivatives such as hydroxypropyl and sulfobutyl ether cyclodextrins such as hydroxypropyl-β-cyclodextrin and sulfobutyl ether β-cyclodextrin. Exemplary buffers for such formulations include carboxylic acid-based buffers such as citrate, lactate and maleate buffer solutions.

Compounds of the invention can also be administered transdermally using known transdermal delivery systems and excipients. For example, the compound can be admixed with permeation enhancers, such as propylene glycol, polyethylene glycol monolaurate, azacycloalkan-2-ones and the like, and incorporated into a patch or similar delivery system. Additional excipients including gelling agents, emulsifiers and buffers, may be used in such transdermal compositions if desired.

Secondary Agents

The compounds of the invention may be useful as the sole treatment of a disease or may be combined with one or more additional therapeutic agents in order to obtain the desired therapeutic effect. Thus, in one embodiment, pharmaceutical compositions of the invention contain other drugs that are co-administered with a compound of the invention. For example, the composition may further comprise one or more drugs (also referred to as “secondary agents(s)”). Such therapeutic agents are well known in the art, and include adenosine receptor antagonists, α-adrenergic receptor antagonists, β₁-adrenergic receptor antagonists, β₂-adrenergic receptor agonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, advanced glycation end product breakers, aldosterone antagonists, aldosterone synthase inhibitors, aminopeptidase N inhibitors, androgens, angiotensin-converting enzyme inhibitors and dual-acting angiotensin-converting enzyme/neprilysin inhibitors, angiotensin-converting enzyme 2 activators and stimulators, angiotensin-II vaccines, anticoagulants, anti-diabetic agents, antidiarrheal agents, anti-glaucoma agents, anti-lipid agents, antinociceptive agents, anti-thrombotic agents, AT₁ receptor antagonists and dual-acting AT₁ receptor antagonist/neprilysin inhibitors and multifunctional angiotensin receptor blockers, bradykinin receptor antagonists, calcium channel blockers, chymase inhibitors, digoxin, diuretics, dopamine agonists, endothelin converting enzyme inhibitors, endothelin receptor antagonists, HMG-CoA reductase inhibitors, estrogens, estrogen receptor agonists and/or antagonists, monoamine reuptake inhibitors, muscle relaxants, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, neprilysin inhibitors, nitric oxide donors, non-steroidal anti-inflammatory agents, N-methyl d-aspartate receptor antagonists, opioid receptor agonists, phosphodiesterase inhibitors, prostaglandin analogs, prostaglandin receptor agonists, renin inhibitors, selective serotonin reuptake inhibitors, sodium channel blocker, soluble guanylate cyclase stimulators and activators, tricyclic antidepressants, vasopressin receptor antagonists, and combinations thereof. Specific examples of these agents are detailed herein.

Accordingly, in yet another aspect of the invention, a pharmaceutical composition comprises a compound of the invention, a second active agent, and a pharmaceutically acceptable carrier. Third, fourth etc. active agents may also be included in the composition. In combination therapy, the amount of compound of the invention that is administered, as well as the amount of secondary agents, may be less than the amount typically administered in monotherapy.

Compounds of the invention may be physically mixed with the second active agent to form a composition containing both agents; or each agent may be present in separate and distinct compositions which are administered to the patient simultaneously or at separate times. For example, a compound of the invention can be combined with a second active agent using conventional procedures and equipment to form a combination of active agents comprising a compound of the invention and a second active agent. Additionally, the active agents may be combined with a pharmaceutically acceptable carrier to form a pharmaceutical composition comprising a compound of the invention, a second active agent and a pharmaceutically acceptable carrier. In this embodiment, the components of the composition are typically mixed or blended to create a physical mixture. The physical mixture is then administered in a therapeutically effective amount using any of the routes described herein.

Alternatively, the active agents may remain separate and distinct before administration to the patient. In this embodiment, the agents are not physically mixed together before administration but are administered simultaneously or at separate times as separate compositions. Such compositions can be packaged separately or may be packaged together in a kit. When administered at separate times, the secondary agent will typically be administered less than 24 hours after administration of the compound of the invention, ranging anywhere from concurrent with administration of the compound of the invention to about 24 hours post-dose. This is also referred to as sequential administration. Thus, a compound of the invention can be orally administered simultaneously or sequentially with another active agent using two tablets, with one tablet for each active agent, where sequential may mean being administered immediately after administration of the compound of the invention or at some predetermined time later (for example, one hour later or three hours later). It is also contemplated that the secondary agent may be administered more than 24 hours after administration of the compound of the invention. Alternatively, the combination may be administered by different routes of administration, that is, one orally and the other by inhalation.

In one embodiment, the kit comprises a first dosage form comprising a compound of the invention and at least one additional dosage form comprising one or more of the secondary agents set forth herein, in quantities sufficient to carry out the methods of the invention. The first dosage form and the second (or third, etc.) dosage form together comprise a therapeutically effective amount of active agents for the treatment or prevention of a disease or medical condition in a patient.

Secondary agent(s), when included, are present in a therapeutically effective amount such that they are typically administered in an amount that produces a therapeutically beneficial effect when co-administered with a compound of the invention. The secondary agent can be in the form of a pharmaceutically acceptable salt, solvate, optically pure stereoisomer, and so forth. The secondary agent may also be in the form of a prodrug, for example, a compound having a carboxylic acid group that has been esterified. Thus, secondary agents listed herein are intended to include all such forms, and are commercially available or can be prepared using conventional procedures and reagents.

In one embodiment, compounds of the invention are administered in combination with an adenosine receptor antagonist, representative examples of which include, but are not limited to, naxifylline, rolofylline, SLV-320, theophylline, and tonapofylline.

In one embodiment, compounds of the invention are administered in combination with an α-adrenergic receptor antagonist, representative examples of which include, but are not limited to, doxazosin, prazosin, tamsulosin, and terazosin.

Compounds of the invention may also be administered in combination with a β₁-adrenergic receptor antagonist (“β₁-blockers”). Representative β₁-blockers include, but are not limited to, acebutolol, alprenolol, amosulalol, arotinolol, atenolol, befunolol, betaxolol, bevantolol, bisoprolol, bopindolol, bucindolol, bucumolol, bufetolol, bufuralol, bunitrolol, bupranolol, bubridine, butofilolol, carazolol, carteolol, carvedilol, celiprolol, cetamolol, cloranolol, dilevalol, epanolol, esmolol, indenolol, labetolol, levobunolol, mepindolol, metipranolol, metoprolol such as metoprolol succinate and metoprolol tartrate, moprolol, nadolol, nadoxolol, nebivalol, nipradilol, oxprenolol, penbutolol, perbutolol, pindolol, practolol, pronethalol, propranolol, sotalol, sufinalol, talindol, tertatolol, tilisolol, timolol, toliprolol, xibenolol, and combinations thereof. In one particular embodiment, the β₁-antagonist is selected from atenolol, bisoprolol, metoprolol, propranolol, sotalol, and combinations thereof. Typically, the β₁-blocker will be administered in an amount sufficient to provide from about 2-900 mg per dose.

In one embodiment, compounds of the invention are administered in combination with a β₂-adrenergic receptor agonist, representative examples of which include, but are not limited to, albuterol, bitolterol, fenoterol, formoterol, indacaterol, isoetharine, levalbuterol, metaproterenol, pirbuterol, salbutamol, salmefamol, salmeterol, terbutaline, vilanterol, and the like Typically, the β₂-adrenergic receptor agonist will be administered in an amount sufficient to provide from about 0.05-500 μg per dose.

In one embodiment, compounds of the invention are administered in combination with an advanced glycation end product (AGE) breaker, examples of which include, by way of illustration and not limitation, alagebrium (or ALT-711), and TRC4149.

In another embodiment, compounds of the invention are administered in combination with an aldosterone antagonist, representative examples of which include, but are not limited to, eplerenone, spironolactone, and combinations thereof. Typically, the aldosterone antagonist will be administered in an amount sufficient to provide from about 5-300 mg per day.

In one embodiment, compounds of the invention are administered in combination with an aminopeptidase N or dipeptidyl peptidase III inhibitor, examples of which include, by way of illustration and not limitation, bestatin and PC18 (2-amino-4-methylsulfonyl butane thiol, methionine thiol).

Compounds of the invention can also be administered in combination with an angiotensin-converting enzyme (ACE) inhibitor. Representative ACE inhibitors include, but are not limited to, accupril, alacepril, benazepril, benazeprilat, captopril, ceranapril, cilazapril, delapril, enalapril, enalaprilat, fosinopril, fosinoprilat, imidapril, lisinopril, moexipril, monopril, moveltopril, pentopril, perindopril, quinapril, quinaprilat, ramipril, ramiprilat, saralasin acetate, spirapril, temocapril, trandolapril, zofenopril, and combinations thereof. In a particular embodiment, the ACE inhibitor is selected from: benazepril, captopril, enalapril, lisinopril, ramipril, and combinations thereof. Typically, the ACE inhibitor will be administered in an amount sufficient to provide from about 1-150 mg per day.

In another embodiment, compounds of the invention are administered in combination with a dual-acting angiotensin-converting enzyme/neprilysin (ACE/NEP) inhibitor, examples of which include, but are not limited to: AVE-0848 ((4S,7S,12bR)-7-[3-methyl-2(S)-sulfanylbutyramido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]-benzazepine-4-carboxylic acid); AVE-7688 (ilepatril) and its parent compound; BMS-182657 (2-[2-oxo-3(S)-[3-phenyl-2(S)-sulfanylpropionamido]-2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl]acetic acid); CGS-35601 (N-[1-[4-methyl-2(S)-sulfanylpentanamido]cyclopentylcarbonyl]-L-tryptophan); fasidotril; fasidotrilate; enalaprilat; ER-32935 ((3R,6S,9aR)-6-[3(S)-methyl-2(S)-sulfanylpentanamido]-5-oxoperhydrothiazolo[3,2-a]azepine-3-carboxylic acid); gempatrilat; MDL-101264 ((4S,7S,12bR)-7-[2(S)-(2-morpholinoacetylthio)-3-phenylpropionamido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]benzazepine-4-carboxylic acid); MDL-101287 ([4S-[4α,7α(R*), 12bβ]]-7-[2-(carboxymethyl)-3-phenylpropionamido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]benzazepine-4-carboxylic acid); omapatrilat; RB-105 (N-[2(S)-(mercaptomethyl)-3(R)-phenylbutyl]-L-alanine); sampatrilat; SA-898 ((2R,4R)—N-[2-(2-hydroxyphenyl)-3-(3-mercaptopropionyl)thiazolidin-4-ylcarbonyl]-L-phenylalanine); Sch-50690 (N-[1(S)-carboxy-2-[N2-(methanesulfonyl)-L-lysylamino]ethyl]-L-valyl-L-tyrosine); and combinations thereof, may also be included. In one particular embodiment, the ACE/NEP inhibitor is selected from: AVE-7688, enalaprilat, fasidotril, fasidotrilate, omapatrilat, sampatrilat, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an angiotensin-converting enzyme 2 (ACE2) activator or stimulator.

In one embodiment, compounds of the invention are administered in combination with an angiotensin-II vaccine, examples of which include, but are not limited to ATR12181 and CYT006-AngQb.

In one embodiment, compounds of the invention are administered in combination with an anticoagulant, representative examples of which include, but are not limited to: coumarins such as warfarin; heparin; and direct thrombin inhibitors such as argatroban, bivalirudin, dabigatran, and lepirudin.

In yet another embodiment, compounds of the invention are administered in combination with an anti-diabetic agent. Representative anti-diabetic agents include injectable drugs as well as orally effective drugs, and combinations thereof. Examples of injectable drugs include, but are not limited to, insulin and insulin derivatives. Examples of orally effective drugs include, but are not limited to: biguanides such as metformin; glucagon antagonists; α-glucosidase inhibitors such as acarbose and miglitol; dipeptidyl peptidase IV inhibitors (DPP-IV inhibitors) such as alogliptin, denagliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin; meglitinides such as repaglinide; oxadiazolidinediones; sulfonylureas such as chlorpropamide, glimepiride, glipizide, glyburide, and tolazamide; thiazolidinediones such as pioglitazone and rosiglitazone; and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with antidiarrheal treatments. Representative treatment options include, but are not limited to, oral rehydration solutions (ORS), loperamide, diphenoxylate, and bismuth sabsalicylate.

In yet another embodiment, a compound of the invention is administered in combination with an anti-glaucoma agent. Representative anti-glaucoma agents include, but are not limited to: α-adrenergic agonists such as brimonidine; β₁-adrenergic receptor antagonists; topical β₁-blockers such as betaxolol, levobunolol, and timolol; carbonic anhydrase inhibitors such as acetazolamide, brinzolamide, or dorzolamide; cholinergic agonists such as cevimeline and DMXB-anabaseine; epinephrine compounds; miotics such as pilocarpine; and prostaglandin analogs.

In yet another embodiment, compounds of the invention are administered in combination with an anti-lipid agent. Representative anti-lipid agents include, but are not limited to: cholesteryl ester transfer protein inhibitors (CETPs) such as anacetrapib, dalcetrapib, and torcetrapib; statins such as atorvastatin, fluvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin; and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an anti-thrombotic agent. Representative anti-thrombotic agents include, but are not limited to: aspirin; anti-platelet agents such as clopidogrel, prasugrel, and ticlopidine; heparin, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an AT₁ receptor antagonist, also known as angiotensin II type 1 receptor blockers (ARBs). Representative ARBs include, but are not limited to, abitesartan, azilsartan (e.g., azilsartan medoxomil), benzyllosartan, candesartan, candesartan cilexetil, elisartan, embusartan, enoltasosartan, eprosartan, EXP3174, fonsartan, forasartan, glycyllosartan, irbesartan, isoteoline, losartan, medoximil, milfasartan, olmesartan (e.g., olmesartan medoxomil), opomisartan, pratosartan, ripisartan, saprisartan, saralasin, sarmesin, TAK-591, tasosartan, telmisartan, valsartan, zolasartan, and combinations thereof. In a particular embodiment, the ARB is selected from azilsartan medoxomil, candesartan cilexetil, eprosartan, irbesartan, losartan, olmesartan medoxomil, irbesartan, saprisartan, tasosartan, telmisartan, valsartan, and combinations thereof. Exemplary salts and/or prodrugs include candesartan cilexetil, eprosartan mesylate, losartan potassium salt, and olmesartan medoxomil. Typically, the ARB will be administered in an amount sufficient to provide from about 4-600 mg per dose, with exemplary daily dosages ranging from 20-320 mg per day.

Compounds of the invention may also be administered in combination with a dual-acting agent, such as an AT₁ receptor antagonist/neprilysin inhibitor (ARB/NEP) inhibitor, examples of which include, but are not limited to, compounds described in U.S. Publication Nos. 2008/0269305 and 2009/0023228, both to Allegretti et al. filed on Apr. 23, 2008, such as the compound, 4′-{2-ethoxy-4-ethyl-5-[((S)-2-mercapto-4-methylpentanoylamino)-methyl]imidazol-1-ylmethyl}-3′-fluorobiphenyl-2-carboxylic acid.

Compounds of the invention may also be administered in combination with multifunctional angiotensin receptor blockers as described in Kurtz & Klein (2009) Hypertension Research 32:826-834.

In one embodiment, compounds of the invention are administered in combination with a bradykinin receptor antagonist, for example, icatibant (HOE-140). It is expected that this combination therapy may present the advantage of preventing angioedema or other unwanted consequences of elevated bradykinin levels.

In one embodiment, compounds of the invention are administered in combination with a calcium channel blocker. Representative calcium channel blockers include, but are not limited to, amlodipine, anipamil, aranipine, barnidipine, bencyclane, benidipine, bepridil, clentiazem, cilnidipine, cinnarizine, diltiazem, efonidipine, elgodipine, etafenone, felodipine, fendiline, flunarizine, gallopamil, isradipine, lacidipine, lercanidipine, lidoflazine, lomerizine, manidipine, mibefradil, nicardipine, nifedipine, niguldipine, niludipine, nilvadipine, nimodipine, nisoldipine, nitrendipine, nivaldipine, perhexyline, prenylamine, ryosidine, semotiadil, terodiline, tiapamil, verapamil, and combinations thereof. In a particular embodiment, the calcium channel blocker is selected from amlodipine, bepridil, diltiazem, felodipine, isradipine, lacidipine, nicardipine, nifedipine, niguldipine, niludipine, nimodipine, nisoldipine, ryosidine, verapamil, and combinations thereof. Typically, the calcium channel blocker will be administered in an amount sufficient to provide from about 2-500 mg per dose.

In one embodiment, compounds of the invention are administered in combination with a chymase inhibitor, such as TPC-806 and 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[{3,4-dioxo-1-phenyl-7-(2-pyridyloxy)}-2-heptyl]acetamide (NK3201).

In one embodiment, compounds of the invention are administered in combination with a diuretic. Representative diuretics include, but are not limited to: carbonic anhydrase inhibitors such as acetazolamide and dichlorphenamide; loop diuretics, which include sulfonamide derivatives such as acetazolamide, ambuside, azosernide, bumetanide, butazolamide, chloraminophenamide, clofenamide, clopamide, clorexolone, disulfamide, ethoxolamide, furosemide, mefruside, methazolamide, piretanide, torsemide, tripamide, and xipamide, as well as non-sulfonamide diuretics such as ethacrynic acid and other phenoxyacetic acid compounds such as tienilic acid, indacrinone and quincarbate; osmotic diuretics such as mannitol; potassium-sparing diuretics, which include aldosterone antagonists such as spironolactone, and Na⁺ channel inhibitors such as amiloride and triamterene; thiazide and thiazide-like diuretics such as althiazide, bendroflumethiazide, benzylhydrochlorothiazide, benzthiazide, buthiazide, chlorthalidone, chlorothiazide, cyclopenthiazide, cyclothiazide, epithiazide, ethiazide, fenquizone, flumethiazide, hydrochlorothiazide, hydroflumethiazide, indapamide, methylclothiazide, meticrane, metolazone, paraflutizide, polythiazide, quinethazone, teclothiazide, and trichloromethiazide; and combinations thereof. In a particular embodiment, the diuretic is selected from amiloride, bumetanide, chlorothiazide, chlorthalidone, dichlorphenamide, ethacrynic acid, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, methylclothiazide, metolazone, torsemide, triamterene, and combinations thereof. The diuretic will be administered in an amount sufficient to provide from about 5-50 mg per day, more typically 6-25 mg per day, with common dosages being 6.25 mg, 12.5 mg or 25 mg per day.

Compounds of the invention may also be administered in combination with an endothelin converting enzyme (ECE) inhibitor, examples of which include, but are not limited to, phosphoramidon, CGS 26303, and combinations thereof.

In a particular embodiment, compounds of the invention are administered in combination with an endothelin receptor antagonist. Representative endothelin receptor antagonists include, but are not limited to: selective endothelin receptor antagonists that affect endothelin A receptors, such as avosentan, ambrisentan, atrasentan, BQ-123, clazosentan, darusentan, sitaxentan, and zibotentan; and dual endothelin receptor antagonists that affect both endothelin A and B receptors, such as bosentan, macitentan, tezosentan).

In yet another embodiment, a compound of the invention is administered in combination with one or more HMG-CoA reductase inhibitors, which are also known as statins. Representative statins include, but are not limited to, atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin.

In one embodiment, compounds of the invention are administered in combination with a monoamine reuptake inhibitor, examples of which include, by way of illustration and not limitation, norepinephrine reuptake inhibitors such as atomoxetine, buproprion and the buproprion metabolite hydroxybuproprion, maprotiline, reboxetine, and viloxazine; selective serotonin reuptake inhibitors (SSRIs) such as citalopram and the citalopram metabolite desmethylcitalopram, dapoxetine, escitalopram (e.g., escitalopram oxalate), fluoxetine and the fluoxetine desmethyl metabolite norfluoxetine, fluvoxamine (e.g., fluvoxamine maleate), paroxetine, sertraline and the sertraline metabolite demethylsertraline; dual serotonin-norepinephrine reuptake inhibitors (SNRIs) such as bicifadine, duloxetine, milnacipran, nefazodone, and venlafaxine; and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with a muscle relaxant, examples of which include, but are not limited to: carisoprodol, chlorzoxazone, cyclobenzaprine, diflunisal, metaxalone, methocarbamol, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a natriuretic peptide or analog, examples of which include but are not limited to: carperitide, CD-NP (Nile Therapeutics), CU-NP, nesiritide, PL-3994 (Palatin Technologies, Inc.), ularitide, cenderitide, and compounds described in Ogawa et al (2004) J. Biol. Chem. 279:28625-31. These compounds are also referred to as natriuretic peptide receptor-A (NPR-A) agonists. In another embodiment, compounds of the invention are administered in combination with a natriuretic peptide clearance receptor (NPR-C) antagonist such as SC-46542, cANF (4-23), and AP-811 (Veale (2000) Bioorg Med Chem Lett 10:1949-52). For example, AP-811 has shown synergy when combined with the NEP inhibitor, thiorphan (Wegner (1995) Clin. Exper. Hypert. 17:861-876).

In another embodiment, compounds of the invention are administered in combination with a neprilysin (NEP) inhibitor. Representative NEP inhibitors include, but are not limited to: AHU-377; candoxatril; candoxatrilat; dexecadotril ((+)-N-[2(R)-(acetylthiomethyl)-3-phenylpropionyl]glycine benzyl ester); CGS-24128 (3-[3-(biphenyl-4-yl)-2-(phosphonomethylamino)propionamido]propionic acid); CGS-24592 ((S)-3-[3-(biphenyl-4-yl)-2-(phosphonomethylamino)propionamido]propionic acid); CGS-25155 (N-[9(R)-(acetylthiomethyl)-10-oxo-1-azacyclodecan-2(S)-ylcarbonyl]-4(R)-hydroxy-L-proline benzyl ester); 3-(1-carbamoylcyclohexyl)propionic acid derivatives described in WO 2006/027680 to Hepworth et al. (Pfizer Inc.); JMV-390-1 (2(R)-benzyl-3-(N-hydroxycarbamoyl)propionyl-L-isoleucyl-L-leucine); ecadotril; phosphoramidon; retrothiorphan; RU-42827 (2-(mercaptomethyl)-N-(4-pyridinyl)benzenepropionamide); RU-44004 (N-(4-morpholinyl)-3-phenyl-2-(sulfanylmethyl)propionamide); SCH-32615 ((S)—N—[N-(1-carboxy-2-phenylethyl)-L-phenylalanyl]-3-alanine) and its prodrug SCH-34826 ((S)—N—[N-[1-[[(2,2-dimethyl-1,3-dioxolan-4-yl)methoxy]carbonyl]-2-phenylethyl]-L-phenylalanyl]-β-alanine); sialorphin; SCH-42495 (N-[2(S)-(acetylsulfanylmethyl)-3-(2-methylphenyl)propionyl]-L-methionine ethyl ester); spinorphin; SQ-28132 (N-[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]leucine); SQ-28603 (N-[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]-β-alanine); SQ-29072 (7-[[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]amino]heptanoic acid); thiorphan and its prodrug racecadotril; UK-69578 (cis-4-[[[1-[2-carboxy-3-(2-methoxyethoxy)propyl]cyclopentyl]carbonyl]amino]cyclohexanecarboxylic acid); UK-447,841 (2-{-[3-(4-chlorophenyl)propylcarbamoyl]-cyclopentylmethyl}-4-methoxybutyric acid); UK-505,749 ((R)-2-methyl-3-{1-[3-(2-methylbenzothiazol-6-yl)propylcarbamoyl]cyclopentyl}propionic acid); 5-biphenyl-4-yl-4-(3-carboxypropionylamino)-2-methylpentanoic acid and 5-biphenyl-4-yl-4-(3-carboxypropionylamino)-2-methylpentanoic acid ethyl ester (WO 2007/056546); daglutril [(3S,2′R)-3-{1-[2′-(ethoxycarbonyl)-4′-phenylbutyl]-cyclopentan-1-carbonylamino}-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetic acid] described in WO 2007/106708 to Khder et al. (Novartis AG); and combinations thereof. In a particular embodiment, the NEP inhibitor is selected from AHU-377, candoxatril, candoxatrilat, CGS-24128, phosphoramidon, SCH-32615, SCH-34826, SQ-28603, thiorphan, and combinations thereof. In a particular embodiment, the NEP inhibitor is a compound such as daglutril or CGS-26303 ([N-[2-(biphenyl-4-yl)-(S)-(1H-tetrazol-5-yl)ethyl]amino]methylphosphonic acid), which have activity both as inhibitors of the endothelin converting enzyme (ECE) and of NEP. Other dual acting ECE/NEP compounds can also be used. The NEP inhibitor will be administered in an amount sufficient to provide from about 20-800 mg per day, with typical daily dosages ranging from 50-700 mg per day, more commonly 100-600 or 100-300 mg per day.

In one embodiment, compounds of the invention are administered in combination with a nitric oxide donor, examples of which include, but are not limited to nicorandil; organic nitrates such as pentaerythritol tetranitrate; and sydnonimines such as linsidomine and molsidomine.

In yet another embodiment, compounds of the invention are administered in combination with a non-steroidal anti-inflammatory agent (NSAID). Representative NSAIDs include, but are not limited to: acemetacin, acetyl salicylic acid, alclofenac, alminoprofen, amfenac, amiprilose, amoxiprin, anirolac, apazone, azapropazone, benorilate, benoxaprofen, bezpiperylon, broperamole, bucloxic acid, carprofen, clidanac, diclofenac, diflunisal, diftalone, enolicam, etodolac, etoricoxib, fenbufen, fenclofenac, fenclozic acid, fenoprofen, fentiazac, feprazone, flufenamic acid, flufenisal, fluprofen, flurbiprofen, furofenac, ibufenac, ibuprofen, indomethacin, indoprofen, isoxepac, isoxicam, ketoprofen, ketorolac, lofemizole, lornoxicam, meclofenamate, meclofenamic acid, mefenamic acid, meloxicam, mesalamine, miroprofen, mofebutazone, nabumetone, naproxen, niflumic acid, oxaprozin, oxpinac, oxyphenbutazone, phenylbutazone, piroxicam, pirprofen, pranoprofen, salsalate, sudoxicam, sulfasalazine, sulindac, suprofen, tenoxicam, tiopinac, tiaprofenic acid, tioxaprofen, tolfenamic acid, tolmetin, triflumidate, zidometacin, zomepirac, and combinations thereof. In a particular embodiment, the NSAID is selected from etodolac, flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, meloxicam, naproxen, oxaprozin, piroxicam, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an N-methyl d-aspartate (NMDA) receptor antagonist, examples of which include, by way of illustration and not limitation, including amantadine, dextromethorphan, dextropropoxyphene, ketamine, ketobemidone, memantine, methadone, and so forth.

In still another embodiment, compounds of the invention are administered in combination with an opioid receptor agonist (also referred to as opioid analgesics). Representative opioid receptor agonists include, but are not limited to: buprenorphine, butorphanol, codeine, dihydrocodeine, fentanyl, hydrocodone, hydromorphone, levallorphan, levorphanol, meperidine, methadone, morphine, nalbuphine, nalmefene, nalorphine, naloxone, naltrexone, nalorphine, oxycodone, oxymorphone, pentazocine, propoxyphene, tramadol, and combinations thereof. In certain embodiments, the opioid receptor agonist is selected from codeine, dihydrocodeine, hydrocodone, hydromorphone, morphine, oxycodone, oxymorphone, tramadol, and combinations thereof.

In a particular embodiment, compounds of the invention are administered in combination with a phosphodiesterase (PDE) inhibitor, particularly a PDE-V inhibitor. Representative PDE-V inhibitors include, but are not limited to, avanafil, lodenafil, mirodenafil, sildenafil (Revatio®), tadalafil (Adcirca®), vardenafil (Levitra®), and udenafil.

In another embodiment, compounds of the invention are administered in combination with a prostaglandin analog (also referred to as prostanoids or prostacyclin analogs). Representative prostaglandin analogs include, but are not limited to, beraprost sodium, bimatoprost, epoprostenol, iloprost, latanoprost, tafluprost, travoprost, and treprostinil, with bimatoprost, latanoprost, and tafluprost being of particular interest.

In yet another embodiment, compounds of the invention are administered in combination with a prostaglandin receptor agonist, examples of which include, but are not limited to, bimatoprost, latanoprost, travoprost, and so forth.

Compounds of the invention may also be administered in combination with a renin inhibitor, examples of which include, but are not limited to, aliskiren, enalkiren, remikiren, and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with a selective serotonin reuptake inhibitor (SSRI). Representative SSRIs include, but are not limited to: citalopram and the citalopram metabolite desmethylcitalopram, dapoxetine, escitalopram (e.g., escitalopram oxalate), fluoxetine and the fluoxetine desmethyl metabolite norfluoxetine, fluvoxamine (e.g., fluvoxamine maleate), paroxetine, sertraline and the sertraline metabolite demethylsertraline, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a 5-HT_(1D) serotonin receptor agonist, examples of which include, by way of illustration and not limitation, triptans such as almotriptan, avitriptan, eletriptan, frovatriptan, naratriptan rizatriptan, sumatriptan, and zolmitriptan.

In one embodiment, compounds of the invention are administered in combination with a sodium channel blocker, examples of which include, by way of illustration and not limitation, carbamazepine, fosphenyloin, lamotrignine, lidocaine, mexiletine, oxcarbazepine, phenyloin, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a soluble guanylate cyclase stimulator or activator, examples of which include, but are not limited to ataciguat, riociguat, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a tricyclic antidepressant (TCA), examples of which include, by way of illustration and not limitation, amitriptyline, amitriptylinoxide, butriptyline, clomipramine, demexiptiline, desipramine, dibenzepin, dimetacrine, dosulepin, doxepin, imipramine, imipraminoxide, lofepramine, melitracen, metapramine, nitroxazepine, nortriptyline, noxiptiline, pipofezine, propizepine, protriptyline, quinupramine, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a vasopressin receptor antagonist, examples of which include, by way of illustration and not limitation, conivaptan and tolvaptan.

Combined secondary therapeutic agents may also be helpful in further combination therapy with compounds of the invention. For example, compounds of the invention can be combined with a diuretic and an ARB, or a calcium channel blocker and an ARB, or a diuretic and an ACE inhibitor, or a calcium channel blocker and a statin. Specific examples include, a combination of the ACE inhibitor enalapril (in the maleate salt form) and the diuretic hydrochlorothiazide, which is sold under the mark Vaseretic®, or a combination of the calcium channel blocker amlodipine (in the besylate salt form) and the ARB olmesartan (in the medoxomil prodrug form), or a combination of a calcium channel blocker and a statin, all may also be used with the compounds of the invention. Other therapeutic agents such as α₂-adrenergic receptor agonists and vasopressin receptor antagonists may also be helpful in combination therapy. Exemplary α₂-adrenergic receptor agonists include clonidine, dexmedetomidine, and guanfacine.

The following formulations illustrate representative pharmaceutical compositions of the invention.

Exemplary Hard Gelatin Capsules for Oral Administration

A compound of the invention (50 g), 440 g spray-dried lactose and 10 g magnesium stearate are thoroughly blended. The resulting composition is then loaded into hard gelatin capsules (500 mg of composition per capsule). Alternately, a compound of the invention (20 mg) is thoroughly blended with starch (89 mg), microcrystalline cellulose (89 mg) and magnesium stearate (2 mg). The mixture is then passed through a No. 45 mesh U.S. sieve and loaded into a hard gelatin capsule (200 mg of composition per capsule).

Alternately, a compound of the invention (30 g), a secondary agent (20 g), 440 g spray-dried lactose and 10 g magnesium stearate are thoroughly blended, and processed as described above.

Exemplary Gelatin Capsule Formulation for Oral Administration

A compound of the invention (100 mg) is thoroughly blended with polyoxyethylene sorbitan monooleate (50 mg) and starch powder (250 mg). The mixture is then loaded into a gelatin capsule (400 mg of composition per capsule). Alternately, a compound of the invention (70 mg) and a secondary agent (30 mg) are thoroughly blended with polyoxyethylene sorbitan monooleate (50 mg) and starch powder (250 mg), and the resulting mixture loaded into a gelatin capsule (400 mg of composition per capsule).

Alternately, a compound of the invention (40 mg) is thoroughly blended with microcrystalline cellulose (Avicel PH 103; 259.2 mg) and magnesium stearate (0.8 mg). The mixture is then loaded into a gelatin capsule (Size #1, White, Opaque) (300 mg of composition per capsule).

Exemplary Tablet Formulation for Oral Administration

A compound of the invention (10 mg), starch (45 mg) and microcrystalline cellulose (35 mg) are passed through a No. 20 mesh U.S. sieve and mixed thoroughly. The granules so produced are dried at 50-60° C. and passed through a No. 16 mesh U.S. sieve. A solution of polyvinylpyrrolidone (4 mg as a 10% solution in sterile water) is mixed with sodium carboxymethyl starch (4.5 mg), magnesium stearate (0.5 mg), and talc (1 mg), and this mixture is then passed through a No. 16 mesh U.S. sieve. The sodium carboxymethyl starch, magnesium stearate and talc are then added to the granules. After mixing, the mixture is compressed on a tablet machine to afford a tablet weighing 100 mg.

Alternately, a compound of the invention (250 mg) is thoroughly blended with microcrystalline cellulose (400 mg), silicon dioxide fumed (10 mg), and stearic acid (5 mg). The mixture is then compressed to form tablets (665 mg of composition per tablet).

Alternately, a compound of the invention (400 mg) is thoroughly blended with cornstarch (50 mg), croscarmellose sodium (25 mg), lactose (120 mg), and magnesium stearate (5 mg). The mixture is then compressed to form a single-scored tablet (600 mg of composition per tablet).

Alternately, a compound of the invention (100 mg) is thoroughly blended with cornstarch (100 mg) with an aqueous solution of gelatin (20 mg). The mixture is dried and ground to a fine powder. Microcrystalline cellulose (50 mg) and magnesium stearate (5 mg) are then admixed with the gelatin formulation, granulated and the resulting mixture compressed to form tablets (100 mg of the compound of the invention per tablet).

Exemplary Suspension Formulation for Oral Administration

The following ingredients are mixed to form a suspension containing 100 mg of the compound of the invention per 10 mL of suspension:

Ingredients Amount Compound of the invention 1.0 g Fumaric acid 0.5 g Sodium chloride 2.0 g Methyl paraben 0.15 g Propyl paraben 0.05 g Granulated sugar 25.5 g Sorbitol (70% solution) 12.85 g Veegum ® K (magnesium aluminum silicate) 1.0 g Flavoring 0.035 mL Colorings 0.5 mg Distilled water q.s. to 100 mL

Exemplary Liquid Formulation for Oral Administration

A suitable liquid formulation is one with a carboxylic acid-based buffer such as citrate, lactate and maleate buffer solutions. For example, a compound of the invention (which may be pre-mixed with DMSO) is blended with a 100 mM ammonium citrate buffer and the pH adjusted to pH 5, or is blended with a 100 mM citric acid solution and the pH adjusted to pH 2. Such solutions may also include a solubilizing excipient such as a cyclodextrin, for example the solution may include 10 wt % hydroxypropyl-3-cyclodextrin.

Other suitable formulations include a 5% NaHCO₃ solution, with or without cyclodextrin.

Exemplary Injectable Formulation for Administration by Injection

A compound of the invention (0.2 g) is blended with 0.4 M sodium acetate buffer solution (2.0 mL). The pH of the resulting solution is adjusted to pH 4 using 0.5 N aqueous hydrochloric acid or 0.5 N aqueous sodium hydroxide, as necessary, and then sufficient water for injection is added to provide a total volume of 20 mL. The mixture is then filtered through a sterile filter (0.22 micron) to provide a sterile solution suitable for administration by injection.

Exemplary Compositions for Administration by Inhalation

A compound of the invention (0.2 mg) is micronized and then blended with lactose (25 mg). This blended mixture is then loaded into a gelatin inhalation cartridge. The contents of the cartridge are administered using a dry powder inhaler, for example.

Alternately, a micronized compound of the invention (10 g) is dispersed in a solution prepared by dissolving lecithin (0.2 g) in demineralized water (200 mL). The resulting suspension is spray dried and then micronized to form a micronized composition comprising particles having a mean diameter less than about 1.5 μm. The micronized composition is then loaded into metered-dose inhaler cartridges containing pressurized 1,1,1,2-tetrafluoroethane in an amount sufficient to provide about 10 μg to about 500 μg of the compound of the invention per dose when administered by the inhaler.

Alternately, a compound of the invention (25 mg) is dissolved in citrate buffered (pH 5) isotonic saline (125 mL). The mixture is stirred and sonicated until the compound is dissolved. The pH of the solution is checked and adjusted, if necessary, to pH 5 by slowly adding aqueous 1 N NaOH. The solution is administered using a nebulizer device that provides about 10 μg to about 500 μg of the compound of the invention per dose.

EXAMPLES

The following Preparations and Examples are provided to illustrate specific embodiments of the invention. These specific embodiments, however, are not intended to limit the scope of the invention in any way unless specifically indicated.

The following abbreviations have the following meanings unless otherwise indicated and any other abbreviations used herein and not defined have their standard, generally accepted meaning:

-   -   AcOH acetic acid     -   BOC t-butoxycarbonyl     -   CPME cyclopentyl methyl ether     -   DCC 1,3-Dicyclohexylcarbodiimide     -   DCM dichloromethane or methylene chloride     -   DIPEA N,N-diisopropylethylamine     -   DMA N,N-dimethylacetamide     -   DMAP 4-dimethylaminopyridine     -   DMF N,N-dimethylformamide     -   EDCI N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide     -   Et₃N triethylamine     -   EtOAc ethyl acetate     -   EtOH ethanol     -   HATU N,N,N,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium     -   hexafluorophosphate     -   HCTU         (2-(6-chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium         hexafluorophosphate)     -   HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid     -   HOBt 1-hydroxybenzotriazole     -   Mca (7-methoxycoumarin-4-yl)acyl     -   MeCN acetonitrile     -   MeTHF 2-methyltetrahydrofuran     -   Pd(dppf)₂Cl₂ 1,1-bis(diphenylphosphino)ferrocene palladium         chloride     -   TFA trifluoroacetic acid     -   THF tetrahydrofuran

Unless noted otherwise, all materials, such as reagents, starting materials and solvents, were purchased from commercial suppliers (such as Sigma-Aldrich, Fluka Riedel-de Haën, and the like) and were used without further purification.

Reactions were run under nitrogen atmosphere, unless noted otherwise. The progress of reactions were monitored by thin layer chromatography (TLC), analytical high performance liquid chromatography (anal. HPLC), and mass spectrometry, the details of which are given in specific examples. Solvents used in analytical HPLC were as follows: solvent A was 98% H₂O/2% MeCN/1.0 mL/L TFA; solvent B was 90% MeCN/10% H₂O/1.0 mL/L TFA.

Reactions were worked up as described specifically in each preparation for example; commonly reaction mixtures were purified by extraction and other purification methods such as temperature-, and solvent-dependent crystallization, and precipitation. In addition, reaction mixtures were routinely purified by preparative HPLC, typically using Microsorb C18 and Microsorb BDS column packings and conventional eluents. Progress of reactions was typically measured by liquid chromatography mass spectrometry (LCMS). Characterization of isomers were done by Nuclear Overhauser effect spectroscopy (NOE). Characterization of reaction products was routinely carried out by mass and ¹H-NMR spectrometry. For NMR measurement, samples were dissolved in deuterated solvent (CD₃OD, CDCl₃, or DMSO-d₆), and ¹H-NMR spectra were acquired with a Varian Gemini 2000 instrument (400 MHz) under standard observation conditions. Mass spectrometric identification of compounds was typically conducted using an electrospray ionization method (ESMS) with an Applied Biosystems (Foster City, Calif.) model API 150 EX instrument or an Agilent (Palo Alto, Calif.) model 1200 LC/MSD instrument.

Preparation 1 (2R,4S)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic Acid Ethyl Ester (compound 7) and (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic Acid Ethyl Ester (compound 8)

Step 1: To a solution of (R)-3-biphenyl-4-yl-2-t-butoxycarbonylamino-propionic acid (50 g, 146 mmol), Meldrum's acid (23.3 g, 161 mmol) and DMAP (27.8 g, 227 mmol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 161 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL) and saturated aqueous NaCl (1×200 mL), then dried under refrigeration with MgSO₄ overnight. The solution was evaporated to yield the crude Compound 1 (68 g, light yellow solid). LC-MS: [M+Na]:490, [2M+Na]:957.

Step 2: To a solution of crude Compound 1 (68 g, 147 mmol) in anhydrous DCM (1 L) was added AcOH (96.7 g, 1.6 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (13.9 g, 366 mmol) was added in small portions over 1 hour. After stirring for another 1 hour at −5° C., saturated aqueous NaCl (300 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over MgSO₄, filtered, and evaporated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=5:1) to yield Compound 2 (46 g, light yellow solid). LC-MS: [M+Na]:476, [2M+Na]:929.

Step 3: A solution of Compound 2 (46 g, 101 mmol) in anhydrous toluene (300 mL) was refluxed under nitrogen for 3 hours. After evaporation of the solvent, the residue was purified by chromatography (hexanes:EtOAc=10:1) to yield Compound 3 (27 g, light yellow solid). LC-MS: [M+Na]:374, [2M+Na]:725; ¹H NMR (300 MHz, CDCl3): δ7.64-7.62 (m, 4H), 7.51-7.46 (m, 2H), 7.42-7.39 (m, 1H), 7.39-7.30 (m, 2H), 4.50-4.43 (m, 1H), 3.27-3.89 (m, 1H), 2.88-2.80 (m, 1H), 2.48-2.42 (m, 2H), 2.09-1.88 (m, 2H), 1.66 (s, 9H).

Step 4: A mixture of Compound 3 (27 g, 77 mmol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (40.3 g, 231 mmol) was heated to 80° C. under nitrogen. After stirring for 3 hours at 80° C., the mixture was diluted with EtOAc (300 mL), washed with water (2×150 mL) and saturated aqueous NaCl (2×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 4 (29.7 g, light yellow oil). LC-MS: [M+H]:425, [2M+H]:835.

Step 5: To a solution of crude Compound 4 (29.7 g, 73 mmol) in THF (200 mL) was added 1 M HCl (81 mL) at 0° C. under nitrogen. After stirring for 1 hour at room temperature, the mixture was diluted with EtOAc (100 mL) and adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layer was extracted with EtOAc (2×150 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 5 (29.4 g, yellow oil). LC-MS: [M+Na]:402, [2M+Na]:781.

Step 6: To a solution of Compound 5 (29.4 g, 77 mmol) in anhydrous THF (300 mL) was added anhydrous EtOH (30 mL) and AcOH (92.5 g, 1.5 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₃CN (19.4 g, 308 mmol) was added in small portions over 1 hour. After stirring for one additional hour at −5° C., the mixture was adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layers were extracted with EtOAc (2×200 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=5:1) to yield Compound 6 (11.2 g, light yellow solid). LC-MS: [M+Na]:404, [2M+Na]:785.

Step 7: To a solution of Compound 6 (11.2 g, 29 mmol) in anhydrous EtOH (500 mL) was added anhydrous K₂CO₃ (8.0 g, 58 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred for 16 hours. After filtration, the filtrate was concentrated and the residue was diluted with water (150 mL), DCM (200 mL) and saturated aqueous NaCl (50 mL). After separation, the aqueous layer was extracted with DCM (2×150 mL). The combined organic layers were washed with saturated aqueous NaCl (2×200 mL), dried over MgSO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=5:1) to yield Compounds 7 and 8 (8.3 g, light yellow solid).

Compound 7: LC-MS: [M+Na]=450, [2M+Na]=877; ¹H NMR (300 MHz, CDCl3): δ7.58-7.23 (m, 9H), 4.46-4.43 (d, 1H), 4.20-4.13 (m, 2H), 3.94 (s, 1H), 3.82-3.70 (m, 2H), 2.85-2.70 (m, 3H), 2.25-2.22 (d, 1H), 2.01-1.92 (m, 1H), 1.47 (s, 9H), 1.26-1.24 (m, 3H).

Compound 8: LC-MS: [M+Na]=450, [2M+Na]=877; ¹H NMR (300 MHz, CDCl3): δ7.58-7.55 (m, 4H), 7.50-7.43 (m, 2H), 7.40-7.30 (m, 1H), 7.26-7.23 (m, 1H), 4.46 (m, 1H), 4.21-4.13 (m, 2H), 3.94 (m, 1H), 3.82-3.77 (m, 2H), 2.83-2.81 (d, 2H), 2.66-2.63 (m, 1H), 2.24 (m, 1H), 1.83-1.81 (m, 2H), 1.38 (s, 9H), 1.30-1.25 (m, 3H).

Preparation 2 (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic Acid (R⁷=H: P²=BOC) and (2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic Acid Ethyl Ester (R⁷=—CH₂CH₃; P² removed)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (210 mg) was saponified with LiOH to yield the BOC-protected acid (R⁷=H; P²=BOC) (120 mg). (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (˜180 mg) was subjected to HCl deprotection to yield the amine ester (R⁷=—CH₂CH₃; P² removed) as an HCl salt (120 mg).

Example 1

A. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid ethyl ester (R⁷=—CH₂CH₃) B. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid (R⁷=H)

1,2,3-Triazole-4-carboxylic acid (87.3 mg, 772 μmol, 1.5 eq.) was combined with HATU (293 mg, 772 μmol, 1.5 eq.) and DIPEA (179 μL, 2.0 eq.) and stirred for 5 minutes at room temperature in DCM (3 mL) to yield the activated acid. (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (220 mg, 514 μmol, 1.0 eq.) was combined with DCM and TFA (1 mL each), and stirred at room temperature for 1 hour. The mixture was evaporated and azeotroped with toluene (2×). The activated acid was added and the resulting mixture was stirred for 2 hours. The reaction was quenched with water and extracted with DCM. The layers were separated, and the organic layer was dried and evaporated. Two-thirds of the product was purified by preparative HPLC to yield compound A (R⁷=—CH₂CH₃) (60 mg, 98% purity), MS m/z [M+H]⁺ calc'd for C₂₃H₂₆N₄O₄, 423.40. found 423.2. One-third of the product was hydrolyzed by adding 1 M of NaOH in water (619 μL) in THF (1 mL). The mixture was stirred at room temperature for 1 hour. The solvent was evaporated and the resulting material purified by preparative HPLC to yield compound B (R⁷=H) (35 mg, 99% purity), MS m/z [M+H]⁺ calc'd for C₂₁H₂₂N₄O₄, 395.16. found 395.2.

C. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (R⁷=—CH₂-5-methyl-[1,3]dioxol-2-one)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid (75 mg, 190 μmol, 1.0 eq.), HOBt (76 mg, 560 μmol, 3.0 eq.), and EDCI (100 μL, 560 μmol, 3.0 eq.) were dissolved in DCM (2 mL). After stirring for 10 minutes, 4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one (0.2 g, 1.5 mmol, 8.0 eq.) and 4-methylmorpholine (82 μL, 4.0 eq.) were added. The resulting mixture was stirred at room temperature overnight. The mixture was diluted with DCM, and washed with water and saturated aqueous NaCl. The organic layer was collected and concentrated. MeCN (1.9 mL) and 4 M of HCl in dioxane (190 μL, 4.0 eq.) were added and the resulting mixture was stirred at room temperature for 2 hours. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 1,2,3-Triazole-4-carboxylic acid (25 mg, 220 μmol, 1.2 eq.) and HATU (71 mg, 190 μmol, 1.0 eq.) were dissolved in DMF (1.5 mL), and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (650 μL) and the intermediate HCl salt. The reaction was monitored and after 1 hour an additional equivalent of 1,2,3-triazole-4-carboxylic acid, HATU, and DIPEA was added. The reaction was quenched with water and the product purified by preparative HPLC to yield the title compound (39.5 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₂₆N₄O₇, 507.18. found 507.4.

D. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 2-methoxy-ethyl ester (R⁷=—(CH₂)₂OCH₃)

(2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (20 mg, 39 μmol, 1.0 eq.) was dissolved in 2-methoxyethanol (3 mL) followed by the addition of 4 M of HCl in dioxane (295.0 μL). The mixture was heated and maintained at 60° C. for 4 hours. The mixture was concentrated and purified by preparative HPLC to yield the title compound (10 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₄H₂₈N₄O₅, 453.21. found 453.3.

E. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 2-(2-methoxy-ethoxy)-ethyl ester (R⁷=—(CH₂)₂O(CH₂)₂OCH₃)

(2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (20 mg, 39 μmol, 1.0 eq.) was dissolved in 2-(2-methoxyethoxy)-ethanol, (3 mL) followed by the addition of 4 M of HCl in dioxane (295.0 μL). The mixture was heated and maintained at 60° C. for 4 hours. The mixture was concentrated and purified by preparative HPLC to yield the title compound (13 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₃₂N₄O₆, 497.23. found 497.6.

F. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 1-cyclohexyloxycarbonyloxy-ethyl ester (R⁷=—CH(CH₃)OCOO-cyclohexyl)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid (50 mg, 120 μmol, 1.0 eq.), DMA (1 mL), DIPEA (0.13 mL, 0.75 mmol) and 1-chloroethyl cyclohexyl carbonate (52 mg, 250 μmol, 2.0 eq.) were combined. The reaction vessel was capped and microwaved at 80° C. for 2 hours. The mixture was dried under vacuum, dissolved in MeCN (2 mL), and combined with 4 M of HCl in dioxane (500 μL). The resulting mixture was stirred at room temperature for 30 minutes. The precipitate was filtered and discarded, and the filtrate containing the intermediate was concentrated down and submitted to next step. 1,2,3-triazole-4-carboxylic acid (14 mg, 120 μmol, 0.5 eq.) and HATU (48 mg, 120 μmol, 1.0 eq) were dissolved in DMF (1 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (44 μL) and the intermediate from last step. The mixture was stirred for 5 minutes. The reaction was quenched with water and the product dried under vacuum. The product was then purified by preparative HPLC to yield the title compound (4.8 mg, 95% purity. MS m/z [M+H]⁺ calc'd for C₃₀H₃₆N₄O₇, 565.26. found 565.4.

G. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 1-isopropoxycarbonyloxy-ethyl ester (R⁷=—CH(CH₃)OCOO—CH(CH₃)₂)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid (50 mg, 120 μmol, 1.0 eq.), DMA (1 mL), DIPEA (0.13 mL) and 1-chloroethyl isopropyl carbonate (83 mg, 0.5 mmol, 4.0 eq.) were combined. The reaction vessel was capped and microwaved at 80° C. for 2 hours. The mixture was dried under vacuum, dissolved in MeCN (2 mL), and combined with 4 M of HCl in dioxane (500 μL). The resulting mixture was stirred at room temperature for 30 minutes. The precipitate was filtered and discarded, and the filtrate containing the intermediate was concentrated down and submitted to the next step. 1,2,3-Triazole-4-carboxylic acid (14 mg, 120 μmol, 0.5 eq.) and HATU (48 mg, 120 μmol, 1.0 eq) were dissolved in DMF (1 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (44 μL) and the intermediate from last step. The mixture was stirred for 5 minutes. The reaction was quenched with water and the product dried under vacuum. The product was then purified by preparative HPLC to yield the title compound (6 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₇H₃₂N₄O₇, 525.23. found 525.4.

H. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 2-methanesulfonyl-ethyl ester (R⁷=—(CH₂)₂SO₂CH₃)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid (100 mg, 250 μmol, 1.0 eq.), HOBt (0.1 g, 750 μmol, 3.0 eq.), and EDCI (130 μL, 3.0 eq.) were dissolved in DCM (2 mL). After stirring for 10 minutes, 2-(methylsulfonyl)-ethanol (250 mg, 2.0 mmol, 8.0 eq.) and 4-methylmorpholine (110 μL, 4.0 eq.) were added. The resulting mixture was stirred at room temperature for 1.5 hours. The reaction was quenched with water. The DCM layer was separated, concentrated, and the product purified by flash chromatography (70-100% EtOAc/hexanes over 15 minutes). The clean fractions were combined and concentrated. MeCN (2.5 mL) and 4 M of HCl in dioxane (250 μL, 4.0 eq.) were added and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 1,2,3-Triazole-4-carboxylic acid (28.3 mg, 250 μmol, 1.0 eq.) and HATU (95.2 mg, 250 μmol, 1.0 eq.) were dissolved in DMF (2.0 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (131 μL) and the intermediate HCl salt. After 5 minutes, the reaction was quenched with water and the product purified by preparative HPLC to yield the title compound (64 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₄H₂₈N₄O₆S, 501.17. found 501.4.

I. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-entanoic acid 2-morpholin-4-yl-ethyl ester (R⁷=—O—(CH₂)₂-morpholine)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid (100 mg, 250 μmol, 1.0 eq.), HOBt (0.2 g, 1.5 mmol, 6.0 eq.), and EDCI (260 μL, 6.0 eq.) were dissolved in DCM (2 mL). After stirring for 10 minutes, 4-morpholineethanol (330 mg, 2.5 mmol) was added. The mixture was stirred at room temperature until the reaction was complete (˜3 hours). The mixture was then diluted with DCM and washed with saturated aqueous NaHCO₃. The organic layer was separated, dried, and concentrated. MeCN (2.5 mL) and 4 M of HCl in dioxane (250 μL) were added and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 1,2,3-Triazole-4-carboxylic acid (28.3 mg, 250 μmol, 1.0 eq.) and HATU (95 mg, 250 μmol, 1.0 eq.) were dissolved in DMF (2.0 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (87.2 μL) and the intermediate HCl salt. After 5 minutes, the mixture was diluted with EtOAc then washed with saturated aqueous NaHCO₃. The organic layer was separated, concentrated and purified by preparative HPLC to yield the title compound (60 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₇H₃₃N₅O₅, 508.25. found 508.4.

Example 2

A. (2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid (R⁷=H)

5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (51.8 mg, 351 μmol, 1.5 eq.) and HATU (133 mg, 351 μmol, 1.5 eq.) were dissolved in DMF (3.0 mL), and the resulting mixture was stirred for 5 minutes to yield the activated acid. (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (100 mg, 234 μmol, 1.0 eq.) was dissolved in MeCN (2 mL) followed by the addition of 4 M of HCl in dioxane (0.5 mL, 2.0 mmol). The mixture was stirred at room temperature for 2 hours, then concentrated to dryness. The activated acid was added and the resulting mixture was stirred for 2 minutes, followed by the addition of DIPEA (81.5 μL). The mixture was stirred at room temperature for 1 hour. The reaction was quenched with water, and the solvent removed under vacuum. The dried solid was dissolved in EtOH (2.0 mL) followed by the addition of 1.0 M of LiOH in water (2.0 mL). The mixture was stirred at room temperature for 3 hours, and the reaction was quenched with AcOH. The solvent was removed under vacuum, the residue was dissolved in AcOH/MeCN and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (61 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₁H₂₁ClN₄O₄, 429.13. found 429.4.

Note that as explained herein, compounds such as this can exist in a tautomer form, for example, as (2S,4S)-5-biphenyl-4-yl-4-[(5-chloro-H-[1,2,4]triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid.

B. (2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid ethyl ester (R⁷=—CH₂CH₃)

5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (60.8 mg, 412 μmol, 1.5 eq.) and HATU (157 mg, 412 μmol, 1.5 eq.) were dissolved in DMF (4.0 mL), and the resulting mixture was stirred for 5 minutes at room temperature to yield the activated acid. DIPEA (95.7 μL) and (2S,4S)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid (HCl salt, 100 mg, 275 μmol, 1.0 eq.) were added to the activated acid and the resulting mixture was stirred for 10 minutes. The reaction was quenched with water and the product dried under vacuum. The dried solid was dissolved in AcOH and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (88 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₃H₂₅ClN₄O₄, 457.16. found 457.4.

C. (2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid 2-methoxy-ethyl ester (R⁷=—(CH₂)₂OCH₃)

(2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid (10 mg, 23 μmol, 1.0 eq.) was dissolved in 2-methoxyethanol (0.8 mL) followed by the addition of 4 M of HCl in dioxane (117 μL). The resulting mixture was heated and maintained at 80° C. for about 3.5 hours. The mixture was concentrated and purified by preparative HPLC to yield the title compound (7.2 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₄H₂₇ClN₄O₅, 487.17. found 487.4.

D. (2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid 2-(2-methoxy-ethoxy)-ethyl ester (R⁷=—(CH₂)₂O(CH₂)₂OCH₃)

(2S,4S)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]-triazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid (10 mg, 23 μmol, 1.0 eq.) was dissolved in 2-methoxyethanol (0.8 mL) followed by the addition of 4 M of HCl in dioxane (117 μL). The resulting mixture was heated and maintained at 80° C. for about 6 hours. The mixture was concentrated and purified by preparative HPLC to yield the title compound (6.6 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₆H₃₁ClN₄O₆, 531.19. found 531.4.

Preparation 3 (2S,4S)-4-Amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic Acid Ethyl Ester (compound 11) and (2S,4S)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic Acid (compound 11)

Step 1: To a solution of (R)-3-(4-bromophenyl)-2-t-butoxycarbonylamino propionic acid (50 g, 145 mmol), Meldrum's acid (23 g, 160 mmol) and DMAP (27.8 g, 227 mmol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 161 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL) and saturated aqueous NaCl (1×200 mL), then dried under refrigeration with MgSO₄ overnight. The solution was evaporated to yield the crude Compound 1 (65.9 g, light yellow solid). LC-MS: [M+Na]:493, [2M+Na]:963.

Step 2: To a solution of crude Compound 1 (65.9 g, 140 mmol) in anhydrous DCM (1 L) was added AcOH (92.5 g, 1.5 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (13.2 g, 350 mmol) was added in small portions over 1 hour. After stirring for another 1 hour at −5° C., saturated aqueous NaCl (300 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=6:1) to yield Compound 2 (33 g, light yellow solid). LC-MS: [M+Na]:479, [2M+Na]:935.

Step 3: A solution of Compound 2 (33 g, 72.3 mmol) in anhydrous toluene (300 mL) was refluxed under nitrogen for 3 hours. After evaporation of the solvent, the residue was purified by chromatography (hexanes:EtOAc=10:1) to yield Compound 3 (21 g, light yellow oil). LC-MS: [M+Na]:377, [2M+Na]:731.

Step 4: To a solution of Compound 3 (21 g, 60 mmol) in 1,4-dioxane (250 mL) was added 3-fluorophenylboronic acid (8.8 g, 63 mmol) and Pd(dppf)₂Cl₂ (4.4 g, 6 mmol) at room temperature under nitrogen. After stirring for 10 minutes, a solution of K₂CO₃ (16.6 g, 120 mmol) in water (250 mL) was added. The mixture was heated to 100° C. and stirred overnight. After evaporation of the solvent, water (200 mL) was added and the material was extracted with EtOAc (3×200 mL×3). The combined organic layers were washed with saturated aqueous NaCl (250 mL), dried over Na2SO₄, and concentrated to yield the crude product, which was further purified by column chromatography (hexanes:EtOAc-4:1) to yield Compound 4 (16.2 g, light yellow oil). LC-MS: [M+Na]:392, [2M+Na]:761.

Step 5: A mixture of Compound 4 (16.2 g, 43.8 mmol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (22.9 g, 131 mmol) was heated to 80° C. under nitrogen. After stirring for 3 hours at 80° C., the mixture was diluted with EtOAc (300 mL), washed with water (2×150 mL) and saturated aqueous NaCl (2×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 5 (18.6 g, light yellow oil). LC-MS: [M+H]:425, [2M+H]:849.

Step 6: To a solution of crude Compound 5 (18.6 g, 43.8 mmol) in THF (200 mL) was added 1 M HCl (48 mL) at 0° C. under nitrogen. After stirring for 1 hour at room temperature, the mixture was diluted with EtOAc (100 mL) and adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layer was extracted with EtOAc (2×150 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 6 (17.4 g, yellow oil). LC-MS: [M+Na]:420, [2M+Na]:817.

Step 7: To a solution of Compound 6 (17.4 g, 43.8 mmol) in anhydrous THF (300 mL) was added anhydrous EtOH (30 mL) and AcOH (52.6 g, 867 mmol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₃CN (6.9 g, 110 mmol) was added in small portions over 1 hour. After stirring for one additional hour at −5° C., the mixture was adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layer was extracted with EtOAc (2×200 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=6:1) to yield Compound 7 (6.7 g, light yellow solid). LC-MS: [M+Na]:422, [2M+Na]:821.

Step 8: To a solution of Compound 7 (6.7 g, 16.7 mmol) in anhydrous EtOH (500 mL) was added anhydrous K₂CO₃ (4.6 g, 33.3 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred for 16 hours. After filtration, the filtrate was concentrated and the residue was diluted with water (150 mL), DCM (200 mL) and saturated aqueous NaCl (50 mL). After separation, the aqueous layer was extracted with DCM (2×150 mL). The combined organic layers were washed with saturated aqueous NaCl (2×200 mL), dried over MgSO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=5:1) to yield Compounds 8 and 9 (5.2 g, light yellow solid).

Compound 8, (2R,4S)-4-t-butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid ethyl ester: LC-MS: [M+Na]=468, [2M+Na]=913; ¹H NMR (300 MHz, CDCl₃): δ7.50-7.48 (m, 2H), 7.39-7.34 (m, 3H), 7.27-7.23 (m, 2H), 7.01 (m, 1H), 4.42 (s, 1H), 4.20-4.13 (m, 2H), 3.90 (s, 1H), 3.78-3.74 (m, 2H), 2.84-2.82 (m, 2H), 2.70 (s, 1H), 2.22 (s, 1H), 2.02-1.95 (m, 1H), 1.59-1.50 (m, 1H), 1.39 (s, 9H), 1.27-1.23 (m, 3H).

Compound 9, (2S,4S)-4-t-butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid ethyl ester: LC-MS: [M+Na]=468, [2M+Na]=913; ¹H NMR (300 MHz, CDCl₃): δ7.50-7.48 (m, 2H), 7.39-7.34 (m, 3H), 7.25-7.23 (m, 2H), 7.01 (m, 1H), 4.42 (s, 1H), 4.19-4.13 (m, 2H), 3.90 (s, 1H), 3.79-3.75 (m, 2H), 2.83-2.81 (m, 2H), 2.70 (m, 1H), 2.21 (s, 1H), 1.79-1.74 (m, 2H), 1.37 (s, 9H), 1.29-1.23 (m, 3H).

Compound 9 (700 mg) was dissolved in MeCN (10 mL) and 4 M of HCl in dioxane (2 mL). The resulting mixture was stirred at room temperature for 2 hours, then concentrated to yield Compound 10 as an HCl salt.

Compound 9 (700 mg) was dissolved in EtOH (8 mL) and 1M LiOH (8 mL). The mixture was stirred at room temperature for 1 hour. The mixture was concentrated, then diluted with water and acidified with 1M HCl. The solids were filtered off, dried, and lyophilized to yield Compound 11.

Example 3 A. (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid ethyl ester (R⁷=—CH₂CH₃) B. and (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid (R⁷=H)

5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (29.0 mg, 196 μmol, 1.5 eq.) and HATU (74.7 mg, 196 μmol, 1.5 eq.) were dissolved in DMF (1.9 mL), and the resulting mixture was stirred for 5 minutes at room temperature. DIPEA (45.6 μL) and (2S,4S)-4-Amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid ethyl ester (HCl salt, 50 mg, 130 μmol, 1.0 eq.) were added, and the resulting mixture was stirred for 10 minutes. The mixture was diluted with EtOAc and washed with water. The organic layer was separated and concentrated to yield the ester intermediate compound A. This intermediate was dissolved in EtOH (1.0 mL) and 1 M of LiOH in water (786 μL). The mixture was stirred at room temperature for 1 hour, and the reaction was quenched with AcOH. The product was purified by preparative HPLC to yield the compound B (29.2 mg, 95% purity). MS m/z [M+H]⁺calc'd for C₂₁H₂₀ClFN₄O₄, 447.12. found 447.2.

C. (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid 2-morpholin-4-yl-ethyl ester (R⁷=—O—(CH₂)₂-morpholine)

(2S,4S)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid (150 mg, 359 μmol, 1.0 eq.), HOBt (290 mg, 2.2 mmol, 6.0 eq.), and EDCI (380 μL, 6.0 eq.) were dissolved in DCM (3 mL). After stirring for 10 minutes, 4-morpholineethanol (470 mg, 3.6 mmol) was added. The mixture was stirred at room temperature until the reaction was complete (˜2 hours). The mixture was then diluted with DCM and washed with saturated aqueous NaHCO₃. The organic layer was separated, dried, and concentrated. MeCN (4.5 mL) and 4 M of HCl in dioxane (719 μL) were added and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (79.5 mg, 539 μmol, 1.5 eq.) and HATU (205 mg, 539 μmol, 1.5 eq.) were dissolved in DMF (3.0 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (313 μL) and the intermediate HCl salt. After 5 minutes, the mixture was diluted with EtOAc then washed with saturated aqueous NaHCO₃. The organic layer was separated, concentrated and purified by preparative HPLC to yield the title compound (43 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₇H₃₁ClFN₅O₅, 560.20. found 560.0.

D. (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid 2-methanesulfonyl-ethyl ester (R⁷=—(CH₂)₂SO₂CH₃)

(2S,4S)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid (100 mg, 240 μmol, 1.0 eq.), HOBt (970 mg, 720 μmol, 3.0 eq.), and EDCI (130 μL, 3.0 eq.) were dissolved in DCM (2 mL). After stirring for 10 minutes, 2-(methylsulfonyl)ethanol (240 mg, 1.9 mmol, 8.0 eq.) and 4-methylmorpholine (100 μL, 4.0 eq.) were added. The mixture was then diluted with DCM and washed with saturated aqueous NaHCO₃. The organic layer was separated, dried, and concentrated. MeCN (2.4 mL) and 4 M of HCl in dioxane (240 μL, 4.0 eq.) were added and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (35.3 mg, 240 μmol, 1.0 eq.) and HATU (91.1 mg, 240 μmol, 1.0 eq.) were dissolved in DMF (1.9 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (125 μL) and the intermediate HCl salt. After 5 minutes, the reaction was quenched with water and the product purified by preparative HPLC to yield the title compound (42 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₄H₂₆ClFN₄O₆S, 553.12. found 553.4.

E. (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid 2-methoxy-ethyl ester (R⁷=—(CH₂)₂OCH₃)

(2S,4S)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid (80 mg, 190 μmol, 1.0 eq.) was dissolved in 2-methoxyethanol (2.0 mL) followed by the addition of 4 M of HCl in dioxane. The mixture was heated and maintained at 75° C. for 2 hours. The mixture was dried under vacuum to provide the intermediate HCl salt, which was used in the following coupling step. 5-Chloro-2H-1,2,4-triazole-3-carboxylic acid (28.3 mg, 192 μmol, 1.0 eq.) and HATU (72.9 mg, 192 μmol, 1.0 eq.) were dissolved in DMF (2.0 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (66.8 μL) and the intermediate HCl salt. After 5 minutes, the reaction was quenched with water and the product purified by preparative HPLC to yield the title compound (46 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₄H₂₆ClFN₄O₅, 505.16. found 505.1.

F. (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-entanoic acid 2-(2-methoxyethoxy)ethyl ester (R⁷=—[(CH₂)₂O]₂CH₃)

(2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)amino]-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic acid ethyl ester (60 mg, 0.1 mmol) was dissolved in EtOH (2.0 mL, 34 mmol) and 1 M LiOH in water (0.6 mL, 0.6 mmol), and stirred at room temperature for 1 hour. The mixture was concentrated, diluted with water, and acidified with 1M HCl to pH˜4. The solids were filtered off and dried. A portion of the solid material (10 mg) was dissolved in 2-(2-methoxyethoxy)-ethanol, (2.0 mL, 17 mmol). 4 M HCl in dioxane (0.8 mL, 3.1 mmol) was added and the mixture was heated to at 75° C. for 6 hours. The product was then purified by preparative HPLC to yield the title compound (10 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂H₃₀ClFN₄O₆, 549.18. found 549.2.

Example 4

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, compounds having formula IIIa-I were prepared:

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 1 —OH H H 0 — C₂₁H₂₂N₄O₄ 395.16 395.2 2 —OH H H 1 2′-F C₂₁H₂₁FN₄O₄ 413.15 413.4 3 —OH H H 1 3′-F C₂₁H₂₁FN₄O₄ 413.15 413.5 4 —CH₂CH₃ H H 1 3′-F C₂₃H₂₅FN₄O₄ 441.19 441.4 5 —O(CH₂)₂—OCH₃ H H 1 3′-F C₂₄H₂₇FN₄O₅ 471.20 471.6 6 —[O(CH₂)₂]₂—OCH₃ H H 1 3′-F C₂₆H₃₁FN₄O₆ 515.22 515.4

-   1.     (2R,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   2.     (2S,4S)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   3.     (2S,4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   4.     (2S,4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid ethyl ester -   5.     (2S,4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid 2-methoxy-ethyl ester -   6.     (2S,4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid 2-(2-methoxy-ethoxy)-ethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 7 —OH H —OH 0 — C₂₁H₂₂N₄O₅ 411.16 411.2 8 —OH H —OH 1 2′-F C₂₁H₂₁FN₄O₅ 429.15 429.2 9 —OH H H 1 3′-Cl C₂₁H₂₁ClN₄O₄ 429.13 429.2 10 —OH H —OH 1 3′-Cl C₂₁H₂₁ClN₄O₅ 445.12 445.4

-   7.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   8.     (2S,4S)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   9.     (2S,4S)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxymethyl-4-[(1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   10.     (2S,4S)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 11 —OH H H 0 — C₂₁H₂₂N₄O₄ 395.16 395.2

-   11.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(1H-[1,2,4]triazole-3-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 12 —OH H H 0 — C₂₁H₂₂N₄O₄ 395.16 395.0 13 —OH —CH₃ H 0 — C₂₂H₂₄N₄O₄ 409.18 409.5 14 —OH —OH H 0 — C₂₁H₂₂N₄O₅ 411.16 411.4 15 —OCH₂CH₃ —OH H 0 — C₂₃H₂₆N₄O₅ 439.19 439.4 16 —OH Cl H 1 2′-F C₂₁H₂₀ClFN₄O₄ 447.12 447.2

-   12.     (S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(2H-[1,2,4]triazole-3-carbonyl)-amino]-pentanoic     acid -   13.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-methyl-2H-[1,2,4]triazole-3-carbonyl)-amino]-pentanoic     acid -   14.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-2H-[1,2,4]triazole-3-carbonyl)-amino]-pentanoic     acid -   15.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-2H-[1,2,4]triazole-3-carbonyl)-amino]-pentanoic     acid ethyl ester -   16.     (2S,4S)-4-[(5-Chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-5-(2′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 17 —OH —OH H 0 — C₂₂H₂₃N₃O₅ 410.16 410.4 18 —OH —COOH H 0 — C₂₃H₂₃N₃O₆ 438.16 438.4 19 —OH —C(O)CH₃ H 0 — C₂₄H₂₅N₃O₅ 436.18 436.4 20 —OH —C(O)—N(CH₃)₂ H 0 — C₂₅H₂₈N₄O₅ 465.21 465.4 21 —OH —C(O)—N(CH₃)₂ H 0 — C₂₅H₂₈N₄O₅ 465.21 465.4 22 —OH —C(O)—N(CH₃)—(CH₂)₂OCH₃ H 0 — C₂₇H₃₂N₄O₆ 509.23 509.4 23 —OH —C(O)NH-cyclopropyl H 0 — C₂₆H₂₈N₄O₅ 477.21 477.2 24 —OH

H 0 — C₂₆H₂₈N₄O₅ 477.21 477.4 25 —OH

H 0 — C₂₇H₃₀N₄O₅ 491.22 491.4 26 —OH

H 0 — C₂₇H₃₀N₄O₆ 507.22 507.4 27 —OH 2-chloro-phenyl H 0 — C₂₈H₂₆ClN₃O₄ 504.16 504.4 28 —OH —(CH₂)₃CH₃ H 0 — C₂₆H₃₁N₃O₄ 450.23 450.4 29 —OH 2-chloro-phenyl H 1 3′-F C₂₈H₂₅ClFN₃O₄ 522.15 522.2 30 —OH

H 1 3′-F C₂₇H₂₅FN₄O₄ 489.19 489.2

-   17.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-2H-pyrazole-3-carbonyl)-amino]-pentanoic     acid -   18.     5-((1S,3S)-1-Biphenyl-4-ylmethyl-3-carboxy-4-hydroxy-butylcarbamoyl)-1H-pyrazole-3-carboxylic     acid -   19.     (2S,4S)-4-[(5-Acetyl-2H-pyrazole-3-carbonyl)-amino]-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic     acid -   20.     (2R,4S)-5-Biphenyl-4-yl-4-[(5-dimethylcarbamoyl-2H-pyrazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   21.     (2S,4S)-5-Biphenyl-4-yl-4-[(5-dimethylcarbamoyl-2H-pyrazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   22.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-({5-[(2-methoxy-ethyl)-methyl-carbamoyl]-2H-pyrazole-3-carbonyl}-amino)-pentanoic     acid -   23.     (2S,4S)-5-Biphenyl-4-yl-4-[(5-cyclopropylcarbamoyl-2H-pyrazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   24.     (2S,4S)-4-{[5-(Azetidine-1-carbonyl)-2H-pyrazole-3-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic     acid -   25.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-{[5-(pyrrolidine-1-carbonyl)-2H-pyrazole-3-carbonyl]-amino}-pentanoic     acid -   26.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-{[5-(morpholine-4-carbonyl)-2H-pyrazole-3-carbonyl]-amino}-pentanoic     acid -   27.     (2S,4S)-5-Biphenyl-4-yl-4-{[5-(2-chloro-phenyl)-2H-pyrazole-3-carbonyl]-amino}-2-hydroxymethyl-pentanoic     acid -   28.     (2S,4S)-5-Biphenyl-4-yl-4-[(5-butyl-2H-pyrazole-3-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   29.     (2S,4S)-4-{[5-(2-Chlorophenyl)-2H-pyrazole-3-carbonyl]-amino}-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-pentanoic     acid -   30.     (2S,4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-[(5-pyridin-2-yl-2H-pyrazole-3-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 31 —OH —OH H 0 — C₂₂H₂₃N₃O₅ 410.16 410.4

-   31.     (2S,4S)-5-Biphenyl-4-yl-4-[(2-hydroxy-1H-imidazole-4-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 32 —OH Cl H 0 — C₂₅H₂₃ClN₄O₄ 479.14 479.2 33 —OH F H 0 — C₂₅H₂₃FN₄O₄ 463.17 463.0 34 —OH H —OH 1 3′-F C₂₅H₂₃ClN₄O₅ 495.14 495.0

-   32.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-3H-benzotriazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid

33. (S)-5-Biphenyl-4-yl-4-[(7-fluoro-3H-benzotriazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic acid

-   34.     (2S,4S)-5-(3′-Chloro-biphenyl-4-yl)-4-[(3-hydroxy-3H-benzotriazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 35 —OH —CH₃ —CH₃ 0 — C₂₈H₂₉N₃O₄ 472.22 472.2 36 —OH H Cl 0 — C₂₆H₂₄ClN₃O₄ 478.15 478.1 37 —OCH₂CH₃ H Cl 0 — C₂₈H₂₈ClN₃O₄ 506.18 506.1 38 —OH —CH₃ Cl 0 — C₂₇H₂₆ClN₃O₄ 492.16 492.1 39 —OCH₂CH₃ —CH₃ Cl 0 — C₂₉H₃₀ClN₃O₄ 520.19 520.2 40 —OH —CH₂—CH₃ Cl 0 — C₂₈H₂₈ClN₃O₄ 506.18 506.2

-   35.     (R)-5-Biphenyl-4-yl-4-[(2,7-dimethyl-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   36.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   37.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester -   38.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-2-methyl-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   39.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-2-methyl-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester -   40.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-2-ethyl-3H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 41 —OCH₂CH₃ —CH₂CH₃ Cl 0 — C₃₀H₃₂ClN₃O₄ 534.21 534.2 42 —OCH₂CH₃ —CH₃ —CH₃ 0 — C₃₀H₃₃N₃O₄ 500.25 500.2

-   41.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-2-ethyl-1H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester -   42.     (R)-5-Biphenyl-4-yl-4-[(2,7-dimethyl-H-benzoimidazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 43 —OH H H 0 — C₂₄H₂₃N₅O₄ 446.18 446.0 44 —O—CH₂CH₃ Cl H 0 — C₂₇H₂₇ClN₄O₄ 507.17 507.3

-   43.     (S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(1H-[1,2,3]triazolo[4,5-b]pyridine-6-carbonyl)-amino]-pentanoic     acid -   44.     (R)-5-Biphenyl-4-yl-4-[(7-chloro-3H-benzotriazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴  b  R⁶ Formula calcd found 45 —OH —OH H 0 — C₂₂H₂₂N₂O₆ 411.15 411.2 46 —O—CH₂CH₃ —OH H 0 — C₂₄H₂₆N₂O₆ 439.18 439.4

-   45.     (2S,4S)-5-Biphenyl-4-yl-4-[(3-hydroxy-isoxazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid -   46.     (2S,4S)-5-Biphenyl-4-yl-4-[(3-hydroxy-isoxazole-5-carbonyl)-amino]-2-hydroxymethyl-pentanoic     acid ethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 47 —OH —OH H 0 — C₂₃H₂₃N₃O₅ 422.16 422.2 48 —O—CH₂CH₃ —OH H 0 — C₂₅H₂₇N₃O₅ 450.20 450.2

-   47.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(2-hydroxy-pyrimidine-5-carbonyl)-amino]-pentanoic     acid -   48.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(2-hydroxy-pyrimidine-5-carbonyl)-amino]-pentanoic     acid ethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 49 —OH —OH H 0 — C₂₃H₂₃N₃O₅ 422.16 422.2

-   49.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(6-hydroxy-pyridazine-3-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 50 —OH ═O —OH 0 — C₂₄H₂₃NO₇ 438.15 438.0

-   50.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-4-oxo-4H-pyran-2-carbonyl)-amino]-pentanoic     acid

Preparation 4 [(R)-2-Biphenyl-4-yl-1-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-ylmethyl)-ethyl]-carbamic acid t-butyl Ester

(R)-3-Biphenyl-4-yl-2-t-butoxycarbonylamino-propionic acid (5.0 g, 15 mmol) and 2,2-dimethyl-1,3-dioxane-4,6-dione (2.3 g, 16.1 mmol) were combined in DMAP (3.2 g, 26.4 mmol). Additional DMAP (2.0 g, 16.1 mmol) and DCM (50 mL) was added and the resulting mixture was stirred and cooled to −5° C. (nitrogen purge) for 30 minutes. EDCI (HCl; (3.1 g, 16.1 mmol) was added in portions, while maintaining the internal temperature below 0° C. with stirring. The mixture was then cooled to −5° C., stirred at that temperature for 3 hours, then left at −20° C. overnight. The mixture was then washed with 0.4 M aqueous KHSO₄ (80 mL) and saturated aqueous NaCl (20 mL), then dried over MgSO₄ overnight. The solids were filtered off and the filtrate was then evaporated to dryness to yield crude Compound 1 (3.2 g).

AcOH (8.6 mL) was added to a solution of crude Compound 1 (6.4 g, 14 mmol, 1.0 eq.) in anhydrous MeCN (90 mL) was added AcOH (8.6 mL) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 30 minutes, then sodium borohydride (1.3 g, 34.5 mmol, 2.5 eq.) was added in small portions over 2 hours. After stirring for another 1 hour at −5° C., saturated aqueous NaCl and 1.7 M of NaCl in water (30 mL) was added. The layers were separated and the organic layer was washed with saturated aqueous NaCl (2×30 mL) and water (2×30 mL), dried under MgSO₄, filtered and evaporated, The resulting crude product was further purified by chromatography (5:1 heptane:EtOAc) to yield Compound 2 (1.1 g, 98.4% purity) as a light yellow solid.

Compound 2 (5.0 g, 11 mmol, 1.0 eq.) and K₂CO₃ (1.8 g, 13.2 mmol, 1.2 eq.) were dissolved in DMF (33.9 mL) and cooled to 0° C. with stirring under nitrogen. Methyl iodide (892 μL, 1.3 eq.) was added and the resulting mixture was stirred at 0° C. for 1 hour. The mixture was allowed to warm to room temperature (23° C.) and held overnight. Saturated aqueous NaCl (35 mL) and EtOAc (35 mL) were added, and the resulting mixture was stirred for 2 minutes. The layers were separated and the organic layer was evaporated. The residue was triturated with EtOAc (20 mL). The solid was filtered off and dried under vacuum. The filtrate was concentrated and triturated again with EtOAc to yield the title compound (3.9 g).

Preparation 5 (2S,4R)-5-Biphenyl-4-yl-4-t-butxarbonylamin-2-hydromethyl-2-methyl-pentanoic acid (P²=BOC) and (2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (P² removed)

Distilled water (140 mL) was purged 30 minutes under nitrogen, then cannulated into a vessel containing 0.1 M of samarium diiodide in THF (800 mL), exercising caution not to allow any air to come into contact with solution. While maintaining an atmosphere of nitrogen, a degassed solution of [(R)-2-biphenyl-4-yl-1-(2,2,5-trimethyl-4,6-dioxo-1,3-dioxinan-5-ylmethyl)-ethyl]-carbamic acid t-butyl ester (3.7 g, 8.0 mmol, 1.0 eq.) and THF (100 mL) was added via canula. The resulting mixture was stirred for 15 minutes, then exposed to air. Saturated aqueous NaCl (12 mL), 10% citric acid (6 mL), and EtOAc (30 mL) were added. The mixture was stirred for 5 minutes, then both layers were extracted. The organic layer was dried over Na₂SO₄ and concentrated under vacuum. The crude product was purified by chromatography (330 g gold column, 50% EtOAc with 0.5% AcOH/ether gradient) to yield the BOC-protected acid (P²=BOC) (1.4 g). The BOC-protected acid was dissolved in MeCN (10 mL), followed by the addition of 4N HCl in dioxane (10 mL). The solvent was evaporated and the product azeotroped with toluene (2×) to yield the acid. (P² removed) (1.0 g).

Preparation 6 (2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic Acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl Ester

[(R)-2-Biphenyl-4-yl-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-ylmethyl)-ethyl]-carbamic acid t-butyl ester (400.0 g, 855.5 mmol) was combined with CPME (2 L) to form a slurry. The slurry was cooled at 0° C. and 3.0 M HCl in CPME (2.0 L) was added. The resulting mixture was stirred at room temperature for 24 hours, yielding a free flowing slurry. Filtration and drying yielded Compound 1 as a 93:7 mixture of diastereoisomers (206 g total). Re-slurrying in MeTHF (1 L) at room temperature followed by the addition of CPME (1 L; slurry overnight at room temperature) yielded Compound 2 (170 g; 98% de purity).

Compound 2 (25.0 g, 80.8 mmol) was combined with THF (500 mL) and 4-methylmorpholine (25 mL, 230 mmol). The resulting mixture was cooled at 0° C. (jacket temp set at −5° C.) and isobutyl chloroformate (21.0 mL, 162 mmol) was added dropwise via addition funnel, while maintaining the internal temperature below 5° C. The mixture was stirred at 0° C. for 20 minutes. Sodium tetrahydroborate (12.2 g, 323 mmol) dissolved in water (40 mL) was added dropwise and the mixture was stirred at 0° C. for 20 minutes (>98% conversion). The reaction was quenched with 1M aqueous HCl (300 mL) and the mixture was stirred at room temperature for 1 hour. Most of solvent was distilled off, leaving a white slurry. The slurry was stirred for 60 minutes and then filtered (small particles, slow filtration) to yield Compound 3 as a white solid (23 g; >98% purity).

Compound 3 (300 g, 1.0 mol) and DCM (3.8 L) were combined and the resulting mixture was cooled at 0° C. Dihydropyran (185 mL, 2.0 mol) and p-toluenesulfonic acid (52.5 g, 305 mmol) were added and the mixture was stirred at room temperature for 2 hours. Aqueous NaHCO₃ (10:90, NaHCO₃:water, 3 L) was added and the phases were separated. The organic layer was dried with Na₂SO₄ followed by solvent removal to approximately 500 mL. Into the crude product was added diisopropyl ether (2 L) and seed crystals. The resulting slurry was stirred overnight at room temperature. Filtration and drying yielded crystalline Compound 4 (320 g; >98% purity).

Compound 4 (320.0 g, 843.2 mmol) was dissolved in THF (2.5 L) to yield a clear solution, which was purged with nitrogen. The solution was cooled at 0° C. and 1.0 M sodium bis(trimethylsilyl)amide in THF (920 mL, 920 mmol) was added dropwise over 30 minutes. The mixture was stirred at 0° C. for 15 minutes then di-t-butyldicarbonate (202 g, 926 mmol) dissolved in THF (500 mL) was added dropwise over 1 hour, while maintaining the internal temperature below 5° C. The mixture was allowed to warm to room temperature (>99% conversion to Compound 5). The mixture was cooled to <5° C. followed by the addition of 1.0 M aqueous LiOH (2.5 L, 2.5 mol). The cooling bath was removed and the mixture was stirred overnight at 27° C. (˜4% starting material remaining). The mixture was heated at 35° C. for 4 hours (>98% conversion), then cooled to 15° C. The mixture was diluted with EtOAc (3 L) and saturated aqueous NH₄Cl (0.37:0.63, NH₄Cl:water, 3 L). The phases were separated, and the organic layer was washed with saturated aqueous NH₄Cl (3 L) and saturated aqueous NaCl (3 L). The organic layer dried with Na₂SO₄ (1 kg), followed by solvent removal to yield crude Compound 6 (463 g) as a glassy sticky solid.

Crude Compound 6 (79.4 g) was dissolved in DMF (640 mL). K₂CO₃ (23.8 g, 172 mmol) was added and the resulting mixture was stirred at room temperature for 15 minutes. The mixture was cooled at 0° C. followed by addition of 4-chloromethyl-5-methyl-1,3-dioxol-2-one (20.6 mL, 188 mmol). The mixture was maintained at 0° C. and stirred over 3 hours (˜55% starting material and ˜38% product). The mixture was then stirred at room temperature (20.2° C.) overnight (˜16 hours; starting material was non-detectable). EtOAc (1.5 L) was added. The organic layer was washed with 3 M aqueous NH₄Cl (2×1.5 L) and saturated aqueous NaCl (1.5 L), dried with Na₂SO₄ (40 g), followed by solvent removal to yield crude Compound 7 as a thick oil. The crude Compound 7 was dissolved in DCM (500 ml) followed by the addition of 3.0 M aqueous HCl in CPME (798 mL, 2.4 mol). Seed crystals were added and the resulting mixture was stirred overnight to yield a free flowing slurry. The volume was reduced by half and the resulting slurry was filtered, flasked, and the filter cake was washed with diisopropyl ether to yield the title compound as a off-white solid HCl salt (69.1 g; 96.2% purity).

Example 5

A. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (R⁴=H: R⁷=H)

1,2,3-Triazole-4-carboxylic acid (130 mg, 1.2 mmol, 1.2 eq.) and HATU (400 mg, 1.1 mmol, 1.1 eq.) were dissolved in DIPEA (167 μL) and the resulting mixture was stirred for 5 minutes at room temperature in DMF (0.2 mL). DIPEA (3 eq.) and (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (300 mg, 957 μmol, 1.0 eq.) dissolved in DMF (0.2 mL) was added, and the resulting mixture was stirred for 15 minutes. The reaction was quenched with AcOH and the product was purified by preparative HPLC then lyophilized to yield the title compound (120 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₂H₂₄N₄O₄, 409.18. found 409.4.

Note that as explained herein, compounds such as this can exist in a tautomer form, for example, as (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid.

B. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid ethyl ester (R⁴=H: R⁷=—CH₂CH₃)

1,2,3-Triazole-4-carboxylic acid (11.5 mg, 102 μmol, 1.2 eq.) and HATU (38.6 mg, 102 μmol, 1.2 eq.) were dissolved in DMF (0.9 mL) and stirred at room temperature for 5 minutes. DIPEA (29.5 μL, 2.0 eq.) was added to yield the activated acid. (2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (35 mg, 85 μmol, 1.0 eq.) was dissolved in EtOH and 4 M of HCl in dioxane (423 μL) was added. The mixture was heated to 60° C. overnight, then concentrated to dryness and purified by reverse phase chromatography (5-60% MeCN in water over 18 minutes. The clean fractions were combined and dried under vacuum to dryness, then combined with the activated acid. After 20 minutes, the reaction was quenched with water and the product was dried under vacuum and purified by preparative HPLC to yield the title compound (4 mg, >95% purity. MS m/z [M+H]⁺ calc'd for C₂₄H₂₈N₄O₄, 437.21. found 437.3.

C. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (R⁴=H: R⁷=—CH₂-5-methyl-[1,3]dioxol-2-one

(2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (100 mg, 245 μmol, 1.0 eq.), EDCI (52 μL, 294 μmol, 1.2 eq.) and HOBt (39.7 mg, 294 μmol, 1.2 eq.) were dissolved in DCM (5 mL). After stirring for 10 minutes, 4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one (127 mg, 979 μmol, 4.0 eq.) was added. The mixture was stirred for 1 hour and 4-methylmorpholine (40.4 μL, 1.5 eq.) was added. After 1 hour, the crude material was dissolved in AcOH and purified by preparative HPLC to yield the title compound (20 mg). MS m/z [M+H]⁺ calc'd for C₂₇H₂₈N₄O₇, 521.20. found 521.4.

Note that as explained herein, compounds such as this can exist in a tautomer form, for example, as (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester.

Preparation of Crystalline (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester

(2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (50 mg) was dissolved in a minimal amount of EtOAc in a small vial. This vial was placed in a larger vial containing hexanes (vapor diffusion). The larger vial was then capped and allowed to sit overnight, yielding oily glassy droplets. Sonication converted the droplets to a gummy solid. The gummy solid was allowed to sit at room temperature (closed) for 3 days, yielding white crunchy solids the formed on the walls. Sonication yielded fine birefringent needle crystals (used as seed crystals below).

(2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(H-1,2,3-triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-1,3-dioxol-4-ylmethyl ester (18.0 g, 34.6 mmol) was dissolved in MeOH (110 mL, 2700 mmol). Water (100 mL) was slowly added until the solution became cloudy (70 mL). Seeds were added and the mixture was stirred for two hours, yielding a gradually thickening free-flowing slurry. The remaining water was added dropwise and the mixture was stirred overnight at room temperature. The resulting solids were filtered and dried (16.2 g). The product was analyzed by powder X-ray diffraction, differential scanning calorimetry, and thermal gravimetric analysis, as described in the examples below, and determined to be the title crystalline material.

Alternate Preparation of Crystalline (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (350 g, 757.7 mmol) and DCM (4 L) were combined and the resulting mixture was cooled at 0° C. Dihydropyran (173 mL, 1.9 mol) and p-toluenesulfonic acid (19.6 g, 113.6 mmol) were added and the mixture was stirred at 0° C. for 18 hours (>95% conversion). Diisopropyl ether (2 L) was added and the solution was concentrated by rotary evaporation. The resulting slurry was stirred at 4° C. for 4 hours. Filtration and drying yielded Compound 1 (312 g; >98% purity).

1-Trityl-1H-1,2,3-triazole-4-carboxylic acid (2823 g, 796 mmol) was dissolved in THF (6 L). DIPEA (330 mL, 1.9 mol) was added and the resulting mixture was cooled to 0° C. HCTU (380 g, 918 mmol) was added in portions and the mixture was stirred at 0° C. for 15 minutes. Compound 1 (312 g, 612 mmol) was added and the resulting mixture was stirred at 0° C. for 30 minutes (complete conversion). The reaction was quenched with water (5 L) followed by the addition of EtOAc (5 L). The phases were separated, and the organic layer was washed with saturated aqueous NaCl (5 L), dried with Na₂SO₄, and concentrated by rotary evaporation. The crude product was re-slurried in 5 volumes of MeOH to yield Compound 2 (400 g; >98% purity).

Compound 2 (40.0 g, 47.2 mmol) was dissolved in 1.25 M HCl in MeOH (200 mL) and stirred to aid dissolution (>95% deprotection after 2 hours at room temperature). Water (200 mL) was slowly added until the solution became cloudy (100 mL). Seed crystals were added and the solution was stirred at room temperature for 30 minutes to yield a free-flowing slurry. The remaining water was added dropwise and stirred at room temperature overnight. Filtration and drying yielded the title compound as intermediate grade material (30 g). This material was suspended in EtOAc (150 mL) and stirred for 30 minutes. Hexanes (150 mL) was added slowly via addition funnel and the resulting free-flowing slurry was stirred at room temperature overnight. Filtration and drying yielded the title crystalline material (15.3 g; 99.1% purity).

D. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-morpholin-4-yl-ethyl ester (R⁴=H: R⁷=—(CH₂)₂-morpholine)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (300 mg, 726 μmol, 1.0 eq.), EDCI (770 μL, 6.0 eq.) and HOBt (590 mg, 4.4 mmol, 6.0 eq.) were dissolved in DCM (6 mL). After stirring for 2 minutes, 4-morpholineethanol (879 μL, 10.0 eq.) was added, and the resulting mixture was stirred for 3 hours at room temperature. The mixture was diluted with DCM and washed with saturated sodium bicarbonate. The organic layer was separated, dried and concentrated. The material was purified (reverse phase column: 5-60% MeCN in water with 0.05% TFA over 30 min; compound eluted between 35-45% MeCN in water) and the clean fractions were combined and lyophilized. MeCN (7.2 mL) and 4 M of HCl in dioxane (720 μL) were added to the lyophilized material. The resulting mixture was stirred at room temperature for 0.5 hour and then the solvent was removed to yield the intermediate. 1,2,3-Triazole-4-carboxylic acid (82 mg, 726 μmol, 1.0 eq.), HATU (280 mg, 720 μmol, 1.0 eq.) and DMF (5.8 mL) were combined and the resulting mixture was stirred for 5 minutes. DIPEA (505 μL, 4.0 eq.) and the intermediate were added, and the mixture was stirred for 30 minutes. The reaction was quenched with AcOH and the product was purified by preparative HPLC to yield the title compound (60 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₈H₃₅N₅O₅, 522.26. found 522.4.

E. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-methoxy-ethyl ester (R⁴=H: R⁷=—(CH₂)₂OCH₃)

1,2,3-Triazole-4-carboxylic acid (49.7 mg, 439 μmol, 0.8 eq.), DIPEA (230 mL), and HATU (167 mg, 439 μmol, 0.8 eq.) were dissolved in DMF (0.5 mL) and stirred at room temperature for 5 minutes to yield the activated acid. (2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (218 mg, 527 μmol, 1.0 eq.) was dissolved in 4 M of HCl in dioxane (2 mL) and EtOH (4 mL). The mixture was stirred overnight at 70° C. The product was evaporated under vacuum and azeotroped with toluene, then combined with the activated acid. After 15 minutes, the reaction was quenched with AcOH and the product was purified by preparative HPLC and lyophilized to yield the title compound (40 mg). MS m/z [M+H]⁺ calc'd for C₂₅H₃₀N₄O₅, 467.22. found 467.4.

F. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-(2-methoxy-ethoxy)-ethyl ester (R⁴=H: R⁷=—(CH₂)₂O(CH₂)₂OCH₃)

(2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (100 mg, 245 μmol, 1.0 eq) was dissolved in 4 M of HCl in dioxane (0.6 mL) and 2-(2-methoxyethoxy)-ethanol (3 mL). The resulting mixture was stirred overnight at 65° C. The solvent was evaporated and AcOH was added. The product was then purified by preparative HPLC to yield the title compound (70 mg, 95% purity). MS m/z [M+H]⁺calc'd for C₂₇H₃₄N₄O₆, 511.25. found 511.4

G. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-methanesulfonyl-ethyl ester (R⁴=H: R⁷=—(CH₂)₂'SO₂CH₃)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (207 mg, 501 μmol, 1.0 eq.), HOBt (0.2 g, 1.5 mmol, 3.0 eq.), and EDCI (260 μL, 3.0 eq.) were dissolved in DCM (4 mL). After stirring for 2 minutes, 2-(methylsulfonyl)ethanol (0.5 g, 4.0 mmol, 8.0 eq.) and 4-methylmorpholine (220 μL) were added. The mixture was stirred at room temperature for 2 hours. The reaction was quenched with water. The DCM layer was separated and concentrated, then purified by flash chromatography (10-100% EtOAc/hexanes). MeCN (2 mL) and 4 M of HCl in dioxane (0.5 mL) were added and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to provide the intermediate HCl salt, which was used in the following coupling step. 1,2,3-Triazole-4-carboxylic acid (56.6 mg, 501 μmol, 1.0 eq.), HATU (190 mg, 501 μmol, 1.0 eq.) were dissolved in DMF (1 mL) and the resulting solution was stirred for 5 minutes, followed by the addition of DIPEA (262 μL) and the intermediate HCl salt. After 10 minutes, the reaction was quenched with AcOH and the product was purified by preparative HPLC to yield the title compound (28 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₃₀N₄O₆S, 515.19. found 515.4.

H. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid isopropyl ester (R⁴=H: R⁷=—CH(CH₃)₂)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with propan-2-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (38 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₃₀N₄O₄, 451.23. found 451.4.

I. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-dimethylamino-ethyl ester (R⁴=H: R⁷=—(CH₂)₂—N(CH₃)₂)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (125 mg, 302 μmol), HOBt (240 mg, 1.8 mmol), and EDCI (320 μL, 1.8 mmol) were dissolved in DCM and stirred for 2 minutes. N,N-Dimethylaminoethanol (304 μL, 3.0 mmol) was added and the resulting mixture was stirred at room temperature for 3 hours. The mixture was diluted with DCM and washed with saturated aqueous NaHCO₃ solution. The organic layer was separated, dried, concentrated, then purified (Interchim reverse phase chromatography column; 5-70% MeCN in water with 0.5% TFA). The purified material was combined with MeCN (3.0 mL, 58 mmol) and 4 M HCl in dioxane (0.3 mL, 1.2 mmol) and the resulting mixture was stirred at room temperature for 30 minutes. The solvent was removed and azeotroped with toluene (2×) to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-dimethylamino-ethyl ester.

1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-dimethylamino-ethyl ester (93 mg, 240 μmol), predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (30 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₃₃N₅O₄, 480.25. found 480.4.

J. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid butyl ester (R⁴=H: R⁷=—(CH₂)₃CH₃)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with butan-1-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (30 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₃₂N₄O₄, 465.24. found 465.4.

K. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid propyl ester (R⁴=H: R⁷=—(CH₂)₂CH₃)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with propan-1-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (24 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₃₀N₄O₄, 451.23. found 451.4.

L. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-piperidin-1-yl-ethyl ester (R⁴=H: R⁷=—(CH₂)₂-piperidinyl)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (125 mg, 302 μmol), HOBt (240 mg, 1.8 mmol), and EDCI (320 μL, 1.8 mmol) were dissolved in DCM and stirred for 2 minutes. N-(2-Hydroxyethyl)piperidine (401 μL, 3.0 mmol) was added and the resulting mixture was stirred at room temperature for 3 hours. The mixture was diluted with DCM and washed with saturated aqueous NaHCO₃ solution. The organic layer was separated, dried, concentrated, then purified (Interchim reverse phase chromatography column; 5-70% MeCN in water with 0.5% TFA). The purified material was combined with MeCN (3.0 mL, 58 mmol) and 4 M HCl in dioxane (0.3 mL, 1.2 mmol) and the resulting mixture was stirred at room temperature for 30 minutes. The solvent was removed and azeotroped with toluene (2×) to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-piperidin-1-yl-ethyl ester.

1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-piperidin-1-yl-ethyl ester (103 mg, 242 μmol), predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (40 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₉H₃₇N₅O₄, 520.28. found 520.4.

M. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 3-methyl-butyl ester (R⁴=H: R⁷=—(CH₂)₂—CH(CH₃)₂)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with 3-methyl-butan-1-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (28 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₇H₃₄N₄O₄, 479.26. found 479.4.

N. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid pentyl ester (R⁴=H: R⁷=—(CH₂)₄CH₃)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with pentan-1-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (30 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₇H₃₄N₄O₄, 479.26. found 479.4.

O. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid isobutyl ester (R⁴=H: R⁷=—CH₂CH(CH₃)₂)

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (76 mg, 242 μmol) in MeCN (0.4 mL, 8 mmol) and 4 M HCl in 1,4-dioxane (242 μL, 969 μmol) was combined with 2-methyl-propan-1-ol (0.5 mL) at 60° C. The resulting mixture was stirred until solid precipitation was observed (˜30 minutes). The solvent was evaporated under vacuum and the solids were azeotroped in toluene and dried under vacuum. 1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with the dried solids, predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (36 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₃₂N₄O₄, 465.24. found 465.4.

P. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid indan-5-yl ester (R⁴=H: R⁷=indanyl)

(2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (118 mg, 290 μmol), HOBt (118 mg, 871 μmol), and EDCI (154 μL, 871 μmol) were dissolved into DCM and stirred for 15 minutes. 5-Indanol (310 mg, 2.3 mmol) and 4-methylmorpholine (128 μL, 1.2 mmol) were added and the resulting mixture was stirred at room temperature for 2 hours. The reaction was quenched with water and the DCM layer was separated and concentrated. AcOH was added and the product was purified by preparative HPLC to yield the title compound (1.4 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₃₁H₃₂N₄O₄, 525.24. found 5254.

Q. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid oxetan-3-yl ester (R⁴=H: R⁷=oxetanyl)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol), HOBt (98 mg, 720 μmol), and EDCI (130 μL, 720 μmol) were dissolved in DCM and stirred for 15 minutes. Oxetan-3-ol (140 mg, 1.9 mmol) and 4-methylmorpholine (110 μL, 970 μmol) were added and the resulting mixture was stirred at room temperature for 2 hours. The reaction was quenched with water and the DCM layer was separated and concentrated. The product was then purified (Interchim reverse phase chromatography column) and dried under vacuum. The purified material was combined with MeCN (1 mL, 20 mmol) and 4 M HCl in dioxane (240 μL, 970 μmol) and the resulting mixture was stirred at room temperature for 1 hour. The solvent was removed to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid oxetan-3-yl ester.

1,2,3-Triazole-4-carboxylic acid (0.0274 g, 0.242 mmol), DIPEA (169 μL, 969 μmol) and HATU (92 mg, 242 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid oxetan-3-yl ester (89.5 mg, 242 μmol), predissolved in DMF (0.2 mL) and DIPEA (0.5 eq.). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product was purified by preparative HPLC and lyophilized to yield the title compound (17 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₂₈N₄O₅, 465.21. found 465.4.

R. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-morpholin-4-yl-2-oxo-ethyl ester (R⁴=H: R⁷=—CH₂C(O)-morpholinyl)

4-(2-chloroacetyl)morpholine (63 mg, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-morpholin-4-yl-2-oxo-ethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-morpholin-4-yl-2-oxo-ethyl ester (54 mg, 120 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (35 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₈H₃₃N₅O₆, 536.24. found 536.2.

S. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid dimethylcarbamoylmethyl ester (R⁴=H: R⁷=—CH₂C(O)—N(CH₃)₂)

2-Chloro-N,N-dimethylacetamide (40 μL, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid dimethylcarbamoylmethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid dimethylcarbamoylmethyl ester (49 mg, 120 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (51 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₆H₃₁N₅O₅, 494.23. found 494.2.

T. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid methoxycarbonylmethyl ester (R⁴=H: R⁷=—CH₂C(O)—OCH₃)

Chloroacetic acid methyl ester (34 μL, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid methoxycarbonylmethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid methoxycarbonylmethyl ester (47.8 mg, 124 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (18 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₂₈N₄O₆, 481.20. found 481.2.

U. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid acetoxymethyl ester (R⁴=H: R⁷=—CH₂OC(O)CH₃)

Bromomethyl acetate (38 μL, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid acetoxymethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid acetoxymethyl ester (47.8 mg, 124 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (3 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₅H₂₈N₄O₆, 481.20. found 481.2.

V. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid butyryloxymethyl ester (R⁴=H: R⁷=—CH₂OC(O)(CH₂)₂CH₃)

Chloromethyl butyrate (49 μL, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid butyryloxymethyl ester. 1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid butyryloxymethyl ester (51 mg, 120 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (1 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₇H₃₂N₄O₆, 509.23. found 509.4.

W. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid benzyloxycarbonylmethyl ester (R⁴=H: R⁷=—CH₂C(O)O-benzyl)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol), HOBt (98 mg, 726 μmol), and EDCI (128 μL, 726 μmol) were dissolved in DCM (2 mL). After stirring for 15 minutes, benzyl glycolate (274 μL, 1.9 mmol) and 4-methylmorpholine (106 μL, 967 μmol) were added. The resulting mixture was stirred at room temperature overnight, and then the reaction was quenched with water. The DCM layer was separated, concentrated, purified ((Interchim reverse phase chromatography column), and dried under vacuum. The purified material was combined with MeCN (1 mL, 20 mmol) and 4 M HCl in dioxane (240 μL, 970 μmmol) and stirred at room temperature for 1 hour. The solvent was then removed to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid benzyloxycarbonylmethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid benzyloxycarbonylmethyl ester (57.2 mg, 124 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (19 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₃₁H₃₂N₄O₆, 557.23. found 557.2.

X. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 2-(2-oxo-pyrrolidin-1-yl)-ethyl ester (R⁴=H: R⁷=—(CH₂)₂-oxopyrrolidinyl)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol), HOBt (98 mg, 726 μmol), and EDCI (128 μL, 726 μmol) were dissolved in DCM (2 mL). After stirring for 15 minutes, 1-(2-hydroxyethyl)-2-pyrrolidone (218 μL, 1.9 mmol) and 4-methylmorpholine (106 μL, 967 μmol) were added. The resulting mixture was stirred at room temperature overnight, and then the reaction was quenched with water. The DCM layer was separated, concentrated, purified ((Interchim reverse phase chromatography column), and dried under vacuum. The purified material was combined with MeCN (1 mL, 20 mmol) and 4 M HCl in dioxane (240 μL, 970 μmol) and stirred at room temperature for 1 hour. The solvent was then removed to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-(2-oxo-pyrrolidin-1-yl)-ethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 2-(2-oxo-pyrrolidin-1-yl)-ethyl ester (52.6 mg, 124 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (13 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₈H₃₃N₅O₅, 520.25. found 520.4.

Y. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid ethoxycarbonyloxymethyl ester (R⁴=H: R⁷=—CH₂OC(O)OCH₂CH₃)

Chloromethyl ethyl carbonate (54 mg, 387 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol) and Et₃N (35 μL, 254 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified ((Interchim reverse phase chromatography column) the solvent was removed under vacuum to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid ethoxycarbonyloxymethyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid ethoxycarbonyloxymethyl ester (51 mg, 120 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (5 mg; purity 90%). MS m/z [M+H]⁺calc'd for C₂₆H₃₀N₄O₇, 511.21. found 511.6.

Z. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid benzyl ester (R⁴=H: R⁷=benzyl)

(2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (100 mg, 242 μmol), HOBt (98 mg, 726 μmol), and EDCI (128 μL, 726 μmol) were dissolved in DCM (2 mL). After stirring for 15 minutes, benzyl alcohol (200 μL, 1.9 mmol) and 4-methylmorpholine (106 μL, 967 μmol) were added. The resulting mixture was stirred at room temperature overnight, and then the reaction was quenched with water. The DCM layer was separated, concentrated, purified ((Interchim reverse phase chromatography column), and dried under vacuum. The purified material was combined with MeCN (1 mL, 20 mmol) and 4 M HCl in dioxane (240 μL, 970 μmmol) and stirred at room temperature for 1 hour. The solvent was then removed to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid benzyl ester.

1,2,3-Triazole-4-carboxylic acid (14 mg, 124 μmol), DIPEA (86.3 μL, 496 μmol) and HATU (47.1 mg, 124 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid benzyl ester (50 mg, 120 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (13 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₉H₃₀N₄O₄, 499.23. found 499.4.

ZA. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (S)-2-amino-3-methyl-butyryloxymethyl ester (R⁴=H: R⁷=—CH₂OC(O)CH(NH₂)[CH(CH₃)₂])

(S)-2-Benzyloxycarbonylamino-3-methyl-butyric acid chloromethyl ester (232 mg, 774 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (0.2 g, 484 μmol) and Et₃N (71 μL, 508 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified (Interchim reverse phase chromatography column) the solvent was removed under vacuum. MeCN (2 mL) and 4 M HCl in 1,4-dioxane (2 mL, 8 mmol) was added and the resulting mixture was stirred for 30 minutes. The solvent was evaporated under vacuum and the product was azeotroped with toluene (1×) to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (S)-2-benzyloxycarbonylamino-3-methyl-butyryloxymethyl ester.

1,2,3-Triazole-4-carboxylic acid (18 mg, 156 μmol), DIPEA (81.6 μL, 468 μmol) and HATU (59.3 mg, 156 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (S)-2-benzyloxycarbonylamino-3-methyl-butyryloxymethyl ester (90 mg, 160 μmol) dissolved in DMF (1 mL). The resulting mixture was stirred for 20 minutes and the solvent was evaporated. The remaining solid was dissolved in degassed 4.4% formic acid-methanol (5 mL) in a flask containing palladium black (˜100 mg) under nitrogen. The mixture was continuously stirred at room temperature. The mixture was filtered and washed with MeOH. The solvent was evaporated and the product purified by preparative HPLC to yield the title compound (25 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₂₈H₃₅N₅O₆, 538.26. found 538.4.

ZB. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (S)-2-methoxycarbonylamino-3-methyl-butyryloxymethyl ester (R⁴=H; R⁷=—CH₂OC(O)CH[NH(COOCH₃)][CH(CH₃)₂])

(S)-2-Methoxycarbonylamino-3-methyl-butyric acid chloromethyl ester (140 mg, 630 μmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (0.2 g, 484 μmol) and Et₃N (71 μL, 508 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. When the reaction was complete, the product was purified (Interchim reverse phase chromatography column) the solvent was removed under vacuum. MeCN (2 mL) and 4 M HCl in 1,4-dioxane (2 mL, 8 mmol) was added and the resulting mixture was stirred for 30 minutes. The solvent was evaporated under vacuum and the product was azeotroped with toluene (1×) to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (S)-2-methoxycarbonylamino-3-methyl-butyryloxymethyl ester.

1,2,3-Triazole-4-carboxylic acid (45.2 mg, 400 μmol), DIPEA (209 μL, 1.2 mmol) and HCTU (165 mg, 400 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid (S)-2-methoxycarbonylamino-3-methyl-butyryloxymethyl ester (200 mg, 400 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The product purified by preparative HPLC and lyophilized to yield the title compound (15 mg; purity 95%). MS m/z [M+H]⁺ calc'd for C₃₀H₃₇N₅O₈, 596.26. found 596.4.

ZC. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (R)-1-cyclohexyloxycarbonyloxy-ethyl ester (R⁴=H: R⁷=—CH(CH₃)OC(O)O-cyclohexyl) ZD. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid (S)-1-cyclohexyloxycarbonyloxy-ethyl ester (R⁴=H: R⁷=—CH(CH₃)OC(O)O-cyclohexyl)

1-Chloroethyl cyclohexyl carbonate (240 mg, 1.2 mmol) was added to a mixture of (2S,4R)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methyl-pentanoic acid (300 mg, 726 μmol) and Et₃N (106 μL, 762 μmol) in acetone (10 mL). The mixture was refluxed for 24 hours and the reaction monitored for completion. The individual isomers were separated (˜1:1) and purified (Interchim reverse phase chromatography column) the solvent was removed under vacuum. MeCN (2 mL) and 4 M HCl in 1,4-dioxane (3 mL, 10 mmol) was added and the resulting mixture was stirred for 30 minutes. The solvent was evaporated under vacuum and the product was azeotroped with toluene (1×) to yield (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 1-cyclohexyloxycarbonyloxy-ethyl ester.

1,2,3-Triazole-4-carboxylic acid (45.2 mg, 400 μmol), DIPEA (209 μL, 1.2 mmol) and HCTU (165 mg, 400 μmol) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. This was then combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic acid 1-cyclohexyloxycarbonyloxy-ethyl ester (193 mg, 400 μmol). The resulting mixture was stirred for 15 minutes and the reaction was quenched with AcOH. The products were purified and separated by preparative HPLC, then lyophilized to yield to yield compound ZC (20 mg; purity 95%), MS m/z [M+H]⁺ calc'd for C₃₁H₃₈N₄O₇, 579.27. found 579.6, and compound ZD (15 mg; purity 95%), MS m/z [M+H]⁺ calc'd for C₃₁H₃₈N₄O₇, 579.27. found 579.6.

ZE. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(1-phosphonooxymethyl-1H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (R⁴=—CH₂OP(O)(OH)₂: R⁷=—CH₂-5-methyl-[1,3]dioxol-2-one)

To a solution of (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (200 mg, 0.4 mmol) in DMF (1.2 mL, 15.4 mmol) was added K₂CO₃ (58.4 mg, 0.423 mmol) and phosphoric acid di-t-butyl ester chloromethyl ester (99.4 mg, 384 μmol). The resulting mixture was stirred at room temperature until the reaction was complete (overnight), then evaporated under reduced pressure. The crude material was then diluted with EtOAc and a solution of 1M HCl was added to bring the pH to 4-5. The organic layer was extracted twice with EtOAc, washed with water followed by saturated aqueous NaCl, dried over anhydrous MgSO₄, filtrated, and evaporated. The residue was purified by flash chromatography (30-90% EtOAc in Hexanes).

The purified intermediate was dissolved in DCM (739 μL, 11.5 mmol). TFA (0.5 mL, 6 mmol) was added and the solution was stirred at room temperature until the reaction was complete (20 minutes). The mixture reaction was evaporated and purified by preparative HPLC to yield the tile compound and its tautomer, (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3-phosphonooxymethyl-3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (15 g total). MS m/z [M+H]⁺ calc'd for C₂₈H₃₁N₄O₁₁P, 631.17. found 631.0.

ZF. (2S,4R)-5-Biphenyl-4-yl-2-methyl-2-phosphonooxymethyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (R⁴=H: R⁷=—CH₂-5-methyl-[1,3]dioxol-2-one)

A solution of (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (60.0 mg, 115 μmol) in pyridine (103 μL, 1.3 mmol) was added dropwise to a solution of phosphoryl chloride (97 μL, 1.0 mmol) in acetone (338 μL, 4.6 mmol) at 0° C. The resulting mixture was stirred for 5 minutes then purified (Interchim reverse phase chromatography) to yield the title compound (45 mg; purity 100%). MS m/z [M+H]⁺ calc'd for C₂₇H₂₉N₄O₁₀P, 601.16. found 601.1.

ZG. (2S,4R)-2-((S)-2-Amino-3-methyl-butyryloxymethyl)-5-biphenyl-4-yl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (R⁴=H: R⁷=—CH₂-5-methyl-[1,3]dioxol-2-one)

N-(t-Butoxycarbonyl)-L-valine (75 mg, 340 μmol), HOBt (47 mg, 0.34 mmol), EDCI (0.061 mL, 0.34 mmol), and DCM (1.8 mL, 29 mmol) were combined and stirred for 15 minutes. (2S,4R)-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (150 mg, 290 μmol) and 4-methylmorpholine (38 μL, 340 μmol) were added, and the resulting mixture was stirred at room temperature for 3 hours, then evaporated. The crude material was purified by reverse phase column ((Interchim reverse phase chromatography column) to yield the title compound (60.8 mg; purity 98%) as a white solid. MS m/z [M+H]⁺ calc'd for C₃₂H₃₁N₅O₈, 620.26. found 620.3.

Example 6

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, compounds having formula IVa-1 were prepared:

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 1 —OH Cl H C₂₂H₂₃ClN₄O₄ 443.14 443.2 2 —OH —OH H C₂₂H₂₄N₄O₅ 425.17 425.2

-   1.     (2S,4R)-5-Biphenyl-4-yl-4-[(5-chloro-2H-[1,2,4]triazole-3-carbonyl)-amino]-2-hydroxymethyl-2-methyl-pentanoic     acid -   2.     (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-2H-[1,2,4]triazole-3-carbonyl)-amino]-2-methyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 3 —OH H H C₂₂H₂₄N₄O₄ 409.18 409.4

-   3.     (2R,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found  4 —OH H —OH C₂₂H₂₄N₄O₅ 425.17 425.2  5 —OH H —CH₂O— C₃₀H₃₇N₅O₈ 596.26 596.4 C(O)CH— [CH(CH₃)₂]— NHC(O)— OCH₃  6 —OH H benzyl C₂₉H₃₀N₄O₄ 499.23 499.4  7

H —CH₃ C₂₄H₂₆N₄O₄ 435.20 435.2  8

H —CH₃ C₂₅H₂₈N₄O₄ 449.21 449.4  9

H —CH₃ C₂₅H₂₈N₄O₄ 449.21 449.4 10 —OH H —CH₂O— C₂₈H₃₅N₅O₆ 538.26 538.6 C(O)CH— [CH(CH₃)₂]— NH₂ 11

H —CH₂O— C(O)CH— [CH(CH₃)₂]— NH₂ C₃₃H₃₉N₅O₉ 650.27 650.4 12

H —CH₂O— C(O)CH— (phenyl)-NH₂ C₃₆H₃₇N₅O₉ 684.26 684.6 13

H —CH₂O— C(O)CH— (benzyl)-NH₂ C₃₇H₃₉N₅O₉ 698.27 698.4 14

H —CH₂O— C(O)CH₂— NH₂ C₃₀H₃₃N₅O₉ 608.23 608.4

-   4.     (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-2-methyl-pentanoic     acid -   5.     (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-4-([1-((S)-2-methoxycarbonylamino-3-methyl-butyryloxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino)-2-methyl-pentanoic     acid -   6.     (2S,4R)-4-[(1-Benzyl-1H-[1,2,3]triazole-4-carbonyl)-amino]-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid -   7. 1-Methyl-1H-[1,2,3]triazole-4-carboxylic acid     [(R)-2-biphenyl-4-yl-1-((S)-5-methyl-4-oxo-[1,3]dioxan-5-ylmethyl)-ethyl]-amide -   8. 1-Methyl-1H-[1,2,3]triazole-4-carboxylic acid     [(R)-2-biphenyl-4-yl-1-((2S,5S)-2,5-dimethyl-4-oxo-[1,3]dioxan-5-ylmethyl)-ethyl]-amide -   9. 1-Methyl-1H-[1,2,3]triazole-4-carboxylic acid     [(R)-2-biphenyl-4-yl-1-((2R,5S)-2,5-dimethyl-4-oxo-[1,3]dioxan-5-ylmethyl)-ethyl]-amide -   10.     (2S,4R)-4-{[1-((S)-2-Amino-3-methyl-butyryloxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid -   11.     (2S,4R)-4-{[1-((S)-2-Amino-3-methyl-butyryloxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester -   12.     (2S,4R)-4-{[1-((R)-2-Amino-2-phenyl-acetoxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester -   13.     (2S,4R)-4-{[1-((S)-2-Amino-3-phenyl-propionyloxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester -   14.     (2S,4R)-4-{[1-(2-Amino-acetoxymethyl)-1H-[1,2,3]triazole-4-carbonyl]-amino}-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 15 —OH —COOH H C₂₄H₂₅N₃O₆ 452.17 452.2 16 —OH —COCH₃ H C₂₅H₂₇N₃O₅ 450.20 450.2 17 —OH —OH H C₂₃H₂₅N₃O₅ 424.18 424.2

-   15.     5-((R)-1-Biphenyl-4-ylmethyl-3-carboxy-4-hydroxy-3-methyl-butylcarbamoyl)-1H-pyrazole-3-carboxylic     acid -   16.     (2S,4R)-4-[(5-Acetyl-2H-pyrazole-3-carbonyl)-amino]-5-biphenyl-4-yl-2-hydroxymethyl-2-methyl-pentanoic     acid -   17.     (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(5-hydroxy-2H-pyrazole-3-carbonyl)-amino]-2-methyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 18 —OH —OH H C₂₄H₂₅N₃O₅ 436.18 436.4

-   18.     (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(2-hydroxy-pyrimidine-5-carbonyl)-amino]-2-methyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 19 —OH —OH H C₂₃H₂₄N₂O₆ 425.16 425.4 20 —O— —OH H C₂₅H₂₈N₂O₆ 453.19 453.2 CH₂CH₃

-   19.     (2S,4R)-5-Biphenyl-4-yl-4-[(3-hydroxy-isoxazole-5-carbonyl)-amino]-2-hydroxymethyl-2-methyl-pentanoic     acid -   20.     (2S,4R)-5-Biphenyl-4-yl-4-[(3-hydroxy-isoxazole-5-carbonyl)-amino]-2-hydroxymethyl-2-methyl-pentanoic     acid ethyl ester

Preparation 7 [(R)-1-(3′-Fluorobiphenyl-4-ylmethyl)-2-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-ethyl]-carbamic acid t-Butyl Ester

Step 1: To a solution of (R)-2-amino-3-(4-bromophenyl)-propionic acid (50 g, 0.2 mol) in MeCN (700 mL) was added a solution of NaOH (16.4 g, 0.4 mol) in water (700 mL) at −5° C. After stirring for 10 minutes, a solution of (Boc)₂O (44.7 g, 0.2 mol) in MeCN (100 mL) was added. The mixture was warmed to room temperature and stirred overnight. After evaporation of the MeCN, the residue was diluted with DCM (800 mL) and acidified with 1 M HCl to pH 2 at −5° C. The aqueous layer was extracted with DCM (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over anhydrous Na₂SO₄ and concentrated to yield Compound 2 (64.2 g, white solid). LC-MS: [M+Na]:366, [2M+Na]:709.

Step 2: To a solution of Compound 2 (64.2 g, 187 mmol) in 1,4-dioxane (500 mL) was added 3-fluorophenylboronic acid (31.3 g, 224 mmol) and Pd(dppf)₂Cl₂ (13.7 g, 19 mmol) at room temperature under nitrogen. After stirring for 10 min, a solution of K₂CO₃ (51.7 g, 374 mmol) in water (250 mL) was added. The mixture was heated to 100° C. and stirred overnight. After evaporation of the solvent, water (200 mL) was added. The aqueous layer was acidified with 1 M HCl to pH 2 and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (400 mL), dried over anhydrous Na₂SO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc-4:1) to yield Compound 3 (45 g, light yellow oil). LC-MS: [M+Na]:382, [2M+Na]:741.

Step 3: To a solution of Compound 3 (45 g, 125 mmol), Meldrum's acid (23.5 g, 163 mmol), and DMAP (26.0 g, 213 mmol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 163 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL) and saturated aqueous NaCl (1×200 mL), then dried under refrigeration with anhydrous MgSO₄ overnight. The solution was evaporated to yield the crude Compound 4 (57.7 g, light yellow oil). LC-MS: [M+Na]:508, [2M+Na]:993.

Step 4: To a solution of the crude Compound 4 (57.7 g, 119 mmol) in anhydrous DCM (1 L) was added AcOH (78.4 g, 1.3 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (11.3 g, 0.3 mol) was added in small portions over 1 hour. After stirring for a another 1 hour at −5° C., saturated aqueous NaCl (300 mL) was added. The organic layer was washed with water (2×300 mL) and saturated aqueous NaCl (2×300 mL), dried over anhydrous MgSO₄, filtered and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=6:1) to yield Compound 5 (28 g, light yellow oil). LC-MS: [M+Na]:494, [2M+Na]:965.

Step 5: To a solution of Compound 5 (28 g, 60 mmol) in anhydrous DMF (250 mL) was added K₂CO₃ (9.9 g, 72 mmol) and CH₃I (25.6 g, 180 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred overnight. The mixture was diluted with water (3 L) and extracted with EtOAc (3×300 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over anhydrous Na₂SO₄, and concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=5:1) to yield the title compound (11.7 g, light yellow solid). LC-MS: [M+Na]=508, [2M+Na]-993. ¹H NMR (300 MHz, CD₃OD): δ7.52-7.49 (m, 2H), 7.41-7.39 (m, 2H), 7.32-7.27 (m, 3H), 7.07-7.01 (m, 1H), 6.21-6.18 (d, 1H), 3.79 (m, 1H), 2.78-2.61 (m, 2H), 2.35-2.20 (m, 2H), 1.76 (s, 6H), 1.59 (s, 3H), 2.21 (s, 1H), 1.28 (s, 9H).

Preparation 8 (2S,4R)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-entanoic Acid (P²=BOC) and (2S,4R)-4-Amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-pentanoic Acid (P² removed)

Distilled Water (181 mL) was purged 1 hour under nitrogen, then cannulated into a vessel containing 0.1 M of samarium diiodide in THF (800 mL). While maintaining an atmosphere of nitrogen, a similarly degassed solution of [(R)-1-(3′-fluorobiphenyl-4-ylmethyl)-2-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-ethyl]-carbamic acid t-butyl ester (4.9 g, 10.0 mmol, 1.0 eq.) and THF (20 mL) was added via canula. The resulting mixture was stirred for 15 minutes, then exposed to air. The solvent was evaporated, and EtOAc (200 mL), saturated aqueous NaCl (50 mL) and 10% citric acid (20 mL) were added. The mixture was stirred for 5 minutes, then both layers were extracted. The organic layer was dried over Na₂SO₄ and concentrated under vacuum. The crude product was purified by chromatography (330 g gold column, 1:1 ether. EtOAc with 0.5% AcOH) to yield the BOC-protected acid. (P²=BOC) (1.5 g). A portion of the BOC-protected acid was dissolved in 4M HCl in dioxane (6 mL) and MeCN (10 mL). The solvent was evaporated under vacuum to yield the acid (P² removed).

Example 7 5-[(1R,3S)-3-Carboxy-1-(3′-fluorobiphenyl-4-ylmethyl)-4-hydroxy-3-methyl-butylcarbamoyl]-1H-pyrazole-3-carboxylic Acid

3,5-Pyrazoledicarboxylic acid (37.7 mg, 241 μmol, 1.0 eq.), EDCI (42.7 μL, 241 μmol, 1.0 eq.), 4-methylmorpholine (53.1 μL, 2.0 eq.) and 1 HOBt (32.6 mg, 241 μmol, 1.0 eq.) were combined in DMF (0.2 mL) and stirred for 5 minutes at room temperature. A predissolved solution of (2S,4R)-4-amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-pentanoic acid (80 mg, 240 μmol, 1.0 eq.) and 4-methylmorpholine (53.1 μL) in DMF (0.3 mL) was added and the resulting mixture was stirred for 15 minutes. The reaction was quenched by adding AcOH and the product was purified by preparative HPLC and lyophilized to yield the title compound (25 mg). MS m/z [M+H]⁺ calc'd for C₂₄H₂₄FN₃O₆, 470.17. found 470.4.

Example 8

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, compounds having formula IVa-2 were prepared:

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 1 —OH H H 1 3-F C₂₂H₂₃FN₄O₄ 427.17 427.2 2 —OH H H 1 2-F C₂₂H₂₃FN₄O₄ 427.17 427.2 3 —OH H H 1 4-F C₂₂H₂₃FN₄O₄ 427.17 427.2

-   1.     (2S,4R)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   2.     (2S,4R)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid -   3.     (2S,4R)-5-(4′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 4 —OH H —OH 1 2′-F C₂₂H₂₃FN₄O₅ 443.17 443.2

-   4.     (2S,4R)-5-(2′-Fluoro-biphenyl-4-yl)-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-2-methyl-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 5 —OH ═O H 1 2′-F C₂₃H₂₃FN₂O₆ 443.15 443.2

-   5.     (2S,4R)-5-(2′-Fluoro-biphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-[(2-oxo-2,3-dihydro-oxazole-4-carbonyl)-amino]-pentanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ b R⁶ Formula calcd found 6 —OH ═O H 1 2′-F C₂₃H₂₃FN₂O₆ 443.15 443.2

-   6.     (2S,4R)-5-(2′-Fluoro-biphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-[(2-oxo-2,3-dihydro-oxazole-5-carbonyl)-amino]-pentanoic     acid

Preparation 9 (2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-5-methylhexanoic Acid Ethyl Ester

A mixture of (S)-2-(1-biphenyl-4-yl-1-methylethyl)-5-oxo-pyrrolidine-1-carboxylic acid t-butyl ester (8.0 g, 21.2 mmol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (10.0 g, 63.6 mmol) was heated at 80° C. for 3 hours. The mixture was cooled to room temperature and diluted with EtOAc (200 mL). The resulting solution was washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 1 (9.2 g, quantitative) as an oil. ¹H NMR (CDCl₃, 300 MHz) δ 7.53 (m, 9H), 6.95 (s, 1H), 4.60 (br s, 1H), 2.90 (s, 1H), 2.62 (m, 2H), 1.61 (s, 9H), 1.39 (s, 3H), 1.34 (s, 3H).

To a solution of Compound 1 (9.2 g, 21.2 mmol) in THF (80.0 mL) was added 1.0 N HCl (25.0 mL) at 0° C. The mixture was stirred at room temperature for 2 hours and then diluted with EtOAc (100 mL). The resulting mixture was neutralized with saturated aqueous NaHCO₃ and extracted with EtOAc (2×100 mL). The combined extracts were washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 2 (8.6 g, quantitative) as an oil. LC-MS (ESI): m/z 430.1 [M+Na]+.

To a solution of Compound 2 (8.6 g, 21.2 mmol) in THF (150 mL) and EtOH (15.0 mL) was added AcOH (24.3 mL, 0.4 mol) at −5° C. After the mixture was stirred at −5° C. for 30 minutes, NaBH₃CN (5.3 g, 84.8 mmol) was added in small portions over 1 hour. The mixture was stirred at −5° C. for 1 hour and neutralized with saturated aqueous NaHCO₃. The resulting mixture was extracted with EtOAc (2×100 mL). The combined extracts were washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 3 (8.67 g, quantitative) as a foamy solid.

To a solution of Compound 3 (3.5 g, 8.6 mmol) in EtOH (30.0 mL) was added K₂CO₃ (2.4 g, 17.1 mmol) at 0° C. The mixture was stirred at 0° C. for 1 hour and then allowed to warm to room temperature and stirred overnight. The mixture was filtered and the filtrate was concentrated. The residue was treated with water (20 mL) and the resulting mixture was extracted with DCM (3×25 mL). The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated. The residue was purified by flash column chromatography on silica gel (hexanes:EtOAc=6:1) to yield Compound 4 (2.2 g) as a foamy solid. ¹H NMR (CDCl₃, 300 MHz) δ 7.53 (m, 9H), 4.35 (br s, 1H), 4.15 (m, 2H), 3.95 (br s, 1H), 3.65 (m, 2H), 2.61 (br s, 1H), 1.79 (m, 1H), 1.45 (s, 9H), 1.35 (s, 3H), 1.29 (s, 3H), 1.25 (t, 3H). LC-MS (ESI): m/z 478.2 [M+Na]+.

A mixture of Compound 4 (2.2 g, 4.8 mmol) in a 2.0 NHCl-EtOH solution (30.0 mL) was stirred at room temperature for 3 hours. Removal of the solvent under reduced pressure yielded the title compound (1.6 g) as a foamy solid HCl salt. ¹H NMR (DMSO-d6, 300 MHz) δ 8.08 (br s, 3H), 7.55 (m, 9H), 4.95 (br s, 1H), 3.95 (m, 2H), 3.48 (m, 2H), δ 2.75 (br s, 1H), 1.79 (m, 2H), 1.47 (s, 3H), 1.40 (s, 3H), 1.09 (t, 3H). LC-MS (ESI): m/z 356.1 [M+H]+.

Example 9 (2S,4S)-5-Biphenyl-4-yl-4-[(3-hydroxy-isoxazole-5-carbonyl)-amino]-2-hydroxymethyl-5-methyl-hexanoic Acid

3-Hydroxyisoxazole-5-carboxylic acid (15.8 mg, 122 μmol) was combined with HATU (46.6 mg, 122 μmol) in DMF (1.0 mL) and stirred for 5 minutes. DIPEA (53.3 μL, 0.306 mmol) was added, followed by (2S,4S)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-5-methylhexanoic acid ethyl ester (HCl salt; 40 mg, 0.1 mmol). The mixture was stirred at room temperature for 20 minutes. The reaction was quenched with water and extracted with EtOAc. The organic layer was concentrated and 1 M aqueous LiOH (1.0 mL, 1.0 mmol) and EtOH (2.0 mL) were added. The resulting mixture was stirred at room temperature for 2 hours. The reaction was quenched with AcOH and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (40 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₄H₂₆N₂O₆, 439.18. found 439.4.

Example 10

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, compounds having formula IIIa-2 were prepared:

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 1 —OH H —OH C₂₃H₂₆N₄O₅ 439.19 439.4

-   1.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-[(1-hydroxy-1H-[1,2,3]triazole-4-carbonyl)-amino]-5-methyl-hexanoic     acid

MS m/z: [M + H]⁺ Ex. R¹ R³ R⁴ Formula calcd found 2 —OH H H C₂₃H₂₆N₄O₄ 423.20 423.0

-   2.     (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-5-methyl-4-[(3H-[1,2,3]triazole-4-carbonyl)-amino]-hexanoic     acid

Assay 1 In Vitro Assays for the Quantitation of Inhibitor Potencies at Human and Rat NEP, and Human ACE

The inhibitory activities of compounds at human and rat neprilysin (EC 3.4.24.11; NEP) and human angiotensin converting enzyme (ACE) were determined using in vitro assays as described below.

Extraction of NEP Activity from Rat Kidneys

Rat NEP was prepared from the kidneys of adult Sprague Dawley rats. Whole kidneys were washed in cold phosphate buffered saline (PBS) and brought up in ice-cold lysis buffer (1% Triton X-114, 150 mM NaCl, 50 mM tris(hydroxymethyl)aminomethane (Tris) pH 7.5; Bordier (1981) J. Biol. Chem. 256:1604-1607) in a ratio of 5 mL of buffer for every gram of kidney. Samples were homogenized on ice using a polytron hand held tissue grinder. Homogenates were centrifuged at 1000×g in a swinging bucket rotor for 5 minutes at 3° C. The pellet was resuspended in 20 mL of ice cold lysis buffer and incubated on ice for 30 minutes. Samples (15-20 mL) were then layered onto 25 mL of ice-cold cushion buffer (6% w/v sucrose, 50 mM pH 7.5 Tris, 150 mM NaCl, 0.06%, Triton X-114), heated to 37° C. for 3-5 minutes and centrifuged at 1000×g in a swinging bucket rotor at room temperature for 3 minutes. The two upper layers were aspirated off, leaving a viscous oily precipitate containing the enriched membrane fraction. Glycerol was added to a concentration of 50% and samples were stored at −20° C. Protein concentrations were quantitated using a BCA detection system with bovine serum albumin (BSA) as a standard.

Enzyme Inhibition Assays

Recombinant human NEP and recombinant human ACE were obtained commercially (R&D Systems, Minneapolis, Minn., catalog numbers 1182-ZN and 929-ZN, respectively). The fluorogenic peptide substrate Mca-D-Arg-Arg-Leu-Dap-(Dnp)-OH (Medeiros et al. (1997) Braz. J. Med. Biol. Res. 30:1157-62; Anaspec, San Jose, Calif.) and Abz-Phe-Arg-Lys(Dnp)-Pro-OH (Araujo et al. (2000) Biochemistry 39:8519-8525; Bachem, Torrance, Calif.) were used in the NEP and ACE assays respectively.

The assays were performed in 384-well white opaque plates at 37° C. using the fluorogenic peptide substrates at a concentration of 10 M in Assay Buffer (NEP: 50 mM HEPES, pH 7.5, 100 mM NaCl, 0.01% polyethylene glycol sorbitan monolaurate (Tween-20), 10 μM ZnSO₄; ACE: 50 mM HEPES, pH 7.5, 100 mM NaCl, 0.01% Tween-20, 1 M ZnSO₄). The respective enzymes were used at concentrations that resulted in quantitative proteolysis of 1 μM of substrate after 20 minutes at 37° C.

Test compounds were assayed over the range of concentrations from 10 μM to 20 pM. Test compounds were added to the enzymes and incubated for 30 minute at 37° C. prior to initiating the reaction by the addition of substrate. Reactions were terminated after 20 minutes of incubation at 37° C. by the addition of glacial acetic acid to a final concentration of 3.6% (v/v).

Plates were read on a fluorometer with excitation and emission wavelengths set to 320 nm and 405 nm, respectively. Inhibition constants were obtained by nonlinear regression of the data using the equation (GraphPad Software, Inc., San Diego, Calif.):

v=v ₀/[1+(I/K′)]

where v is the reaction rate, v₀ is the uninhibited reaction rate, I is the inhibitor concentration and K′ is the apparent inhibition constant.

Compounds of the invention were tested in this assay and found to have pK_(i) values at human NEP as follows. In general, either the prodrug compounds did not inhibit the enzyme in this in vitro assay, or the prodrugs were not tested (n.d.) since activity would not be expected.

Example pK_(i) 1A n.d. 1B ≧9.0 1C n.d. 1D n.d. 1E n.d. 1F n.d. 1G n.d. 1H n.d. 1I n.d. 2A 8.0-8.9 2B n.d. 2C n.d. 2D n.d. 3A n.d. 3B ≧9.0 3C n.d. 3D n.d. 3E n.d. 3F n.d. 4-1  8.0-8.9 4-2  ≧9.0 4-3  ≧9.0 4-4  n.d. 4-5  n.d. 4-6  n.d. 4-7  ≧9.0 4-8  ≧9.0 4-9  ≧9.0 4-10 ≧9.0 4-11 8.0-8.9 4-12 8.0-8.9 4-13 7.0-7.9 4-14 ≧9.0 4-15 n.d 4-16 ≧9.0 4-17 ≧9.0 4-18 ≧9.0 4-19 8.0-8.9 4-20 7.0-7.9 4-21 8.0-8.9 4-22 8.0-8.9 4-23 8.0-8.9 4-24 ≧9.0 4-25 ≧9.0 4-26 8.0-8.9 4-27 ≧9.0 4-28 ≧9.0 4-29 ≧9.0 4-30 ≧9.0 4-31 7.0-7.9 4-32 8.0-8.9 4-33 ≧9.0 4-34 ≧9.0 4-35 7.0-7.9 4-36 8.0-8.9 4-37 n.d. 4-38 7.0-7.9 4-39 n.d. 4-40 7.0-7.9 4-41 n.d. 4-42 n.d. 4-43 8.0-8.9 4-44 n.d. 4-45 ≧9.0 4-46 n.d. 4-47 ≧9.0 4-48 n.d. 4-49 7.0-7.9 4-50 8.0-8.9 5-A ≧9.0 5-B n.d. 5-C n.d. 5-D n.d. 5-F n.d. 5-F n.d. 5-G n.d. 5-H n.d. 5-I n.d. 5-J n.d. 5-K n.d. 5-L n.d. 5-M n.d. 5-N n.d. 5-O n.d. 5-P n.d. 5-Q n.d. 5-R n.d. 5-S n.d. 5-T n.d. 5-U n.d. 5-V n.d. 5-W n.d. 5-X n.d. 5-Y n.d. 5-Z n.d. 5-ZA n.d. 5-ZB n.d. 5-ZC n.d. 5-ZD n.d. 5-ZE n.d. 5-ZF n.d. 5-ZG n.d. 6-1  8.0-8.9 6-2  7.0-7.9 6-3  7.0-7.9 6-4  ≧9.0 6-5  7.0-7.9 6-6  7.0-7.9 6-7  n.d. 6-8  n.d. 6-9  n.d. 6-10 n.d. 6-11 n.d. 6-12 n.d. 6-13 n.d. 6-14 n.d. 6-15 ≧9.0 6-16 7.0-7.9 6-17 8.0-8.9 6-18 ≧9.0 6-19 ≧9.0 6-20 n.d. 7 ≧9.0 8-1  ≧9.0 8-2  ≧9.0 8-3  7.0-7.9 8-4  ≧9.0 8-5  ≧9.0 8-6  ≧9.0 9 ≧9.0 10-1  ≧9.0 10-2  ≧9.0 n.d. = not determined

Assay 2 Pharmacodynamic (PD) Assay for ACE and NEP Activity in Anesthetized Rats

Male, Sprague Dawley, normotensive rats are anesthetized with 120 mg/kg (i.p.) of inactin. Once anesthetized, the jugular vein, carotid artery (PE 50 tubing) and bladder (flared PE 50 tubing) catheters are cannulated and a tracheotomy is performed (Teflon Needle, size 14 gauge) to facilitate spontaneous respiration. The animals are then allowed a 60 minute stablization period and kept continuously infused with 5 mL/kg/h of saline (0.9%) throughout, to keep them hydrated and ensure urine production. Body temperature is maintained throughout the experiment by use of a heating pad. At the end of the 60 minute stabilization period, the animals are dosed intravenously (i.v.) with two doses of AngI (1.0 μg/kg, for ACE inhibitor activity) at 15 minutes apart. At 15 minutes post-second dose of AngI, the animals are treated with vehicle or test compound. Five minutes later, the animals are additionally treated with a bolus i.v. injection of atrial natriuretic peptide (ANP; 30 μg/kg). Urine collection (into pre-weighted eppendorf tubes) is started immediately after the ANP treatment and continued for 60 minutes. At 30 and 60 minutes into urine collection, the animals are re-challenged with AngI. Blood pressure measurements are done using the Notocord system (Kalamazoo, Mich.). Urine samples are frozen at −20° C. until used for the cGMP assay. Urine cGMP concentrations are determined by Enzyme Immuno Assay using a commercial kit (Assay Designs, Ann Arbor, Mich., Cat. No. 901-013). Urine volume is determined gravimetrically. Urinary cGMP output is calculated as the product of urine output and urine cGMP concentration. ACE inhibition is assessed by quantifying the % inhibition of pressor response to AngI. NEP inhibition is assessed by quantifying the potentiation of ANP-induced elevation in urinary cGMP output.

Assay 3 In Vivo Evaluation of Antihypertensive Effects in the Conscious SHR Model of Hypertension

Spontaneously hypertensive rats (SHR, 14-20 weeks of age) are allowed a minimum of 48 hours acclimation upon arrival at the testing site with free access to food and water. For blood pressure recording, these animals are surgically implanted with small rodent radiotransmitters (telemetry unit; DSI Models TA 11PA-C40 or C50-PXT, Data Science Inc., USA). The tip of the catheter connected to the transmitter is inserted into the descending aorta above the iliac bifurcation and secured in place with tissue adhesive. The transmitter is kept intraperitoneally and secured to the abdominal wall while closing of the abdominal incision with a non-absorbable suture. The outer skin is closed with suture and staples. The animals are allowed to recover with appropriate post operative care. On the day of the experiment, the animals in their cages are placed on top of the telemetry receiver units to acclimate to the testing environment and baseline recording. After at least of 2 hours baseline measurement is taken, the animals are then dosed with vehicle or test compound and followed out to 24 hours post-dose blood pressure measurement. Data is recorded continuously for the duration of the study using Notocord software (Kalamazoo, Mich.) and stored as electronic digital signals. Parameters measured are blood pressure (systolic, diastolic and mean arterial pressure) and heart rate.

Assay 4 In Vivo Evaluation of Antihypertensive Effects in the Conscious DOCA-Salt Rat Model of Hypertension

CD rats (male, adult, 200-300 grams, Charles River Laboratory, USA) are allowed a minimum of 48 hours acclimation upon arrival at the testing site before they are placed on a high salt diet. One week after the start of the high salt diet (8% in food or 1% NaCl in drinking water), a deoxycorticosterone acetate (DOCA) pellet (100 mg, 90 days release time, Innovative Research of America, Sarasota, Fla.) is implanted subcutaneously and unilateral nephrectomy is performed. At this time, the animals are also surgically implanted with small rodent radiotransmitters for blood pressure measurement (see Assay 3 for details). The animals are allowed to recover with appropriate post operative care. Study design, data recording, and parameters measured is similar to that described for Assay 3.

Assay 5 In Vivo Evaluation of Antihypertensive Effects in the Conscious Dahl/SS Rat Model of Hypertension

Male, Dahl salt sensitive rats (Dahl/SS, 6-7 weeks of age from Charles River Laboratory, USA) are allowed at least 48 hours of acclimation upon arrival at the testing site before they were placed on a 8% NaCl high salt diet (TD.92012, Harlan, USA) then surgically implanted with small rodent radiotransmitters for blood pressure measurement (see Assay 3 for details). The animals are allowed to recover with appropriate post operative care. At approximately 4 to 5 weeks from the start of high salt diet, these animals are expected to become hypertensive. Once the hypertension level is confirmed, these animals are used for the study while continued with the high salt diet to maintain their hypertension level. Study design, data recording, and parameters measured is similar to that described in Assay 3.

While the present invention has been described with reference to specific aspects or embodiments thereof, it will be understood by those of ordinary skilled in the art that various changes can be made or equivalents can be substituted without departing from the true spirit and scope of the invention. Additionally, to the extent permitted by applicable patent statutes and regulations, all publications, patents and patent applications cited herein are hereby incorporated by reference in their entirety to the same extent as if each document had been individually incorporated by reference herein. 

1. (canceled)
 2. The compound of claim 27, where X is selected from the group consisting of pyrazole, imidazole, triazole, benzotriazole, furan, pyrrole, tetrazole, pyrazine, thiophene, oxazole, isoxazole, thiazole, isothiazole, oxadiazole, thiadiazole, pyridazine, pyridine, pyrimidine, pyran, benzimidazole, benzoxazole, benzothiazole, pyridylimidazole, and pyridyltriazole.
 3. The compound of claim 2, where X is selected from the group consisting of pyrazole, imidazole, triazole, benzotriazole, oxazole, isoxazole, pyrimidine, pyridazine, benzimidazole, pyran, and pyridyltriazole.
 4. (canceled)
 5. The compound of claim 27, where R¹ is selected from the group consisting of —OR⁷ and —NR⁸R⁹; R⁷ is H; R⁸ is H or —OH; and R⁹ is H.
 6. The compound of claim 27, where: R¹ is —OR⁷; and R⁷ is selected from the group consisting of —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹ is —NR⁸R⁹; R⁸ is selected from the group consisting of —OC(O)R⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is H; or R¹ is —NR⁸R⁹; R⁸ is selected from the group consisting of —OC(O)R⁴, —CH₂COOH, —O-benzyl, pyridyl, and —OC(S)NR¹⁵R¹⁶; and R⁹ is —C₁₋₆alkyl or —C(O)R¹⁷; R¹ is —NR⁸R⁹; R⁸ is selected from H or —OH; and R⁹ is —C₁₋₆alkyl or —C(O)R¹⁷; R¹ is —OR⁷ and R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—; or R¹ is —NR⁸R⁹ and R^(2a) is taken together with R⁸ to form —CH₂O—C(O)—.
 7. The compound of claim 27, where R¹ is —OR⁷; R⁷ is selected from the group consisting of H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from the group consisting of —C₁₋₆alkyl, —O—C₁₋₆alkyl, —O—C₃₋₇cycloalkyl, —CH[CH(CH₃)₂]—NH₂, and —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl; R¹² and R¹³ are —C₁₋₆alkyl or are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³¹ is selected from the group consisting of —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —CH₃.
 8. The compound of claim 27, where R^(2a) is —CH₂OH and R^(2b) is H.
 9. The compound of claim 27, where R^(2a) is selected from the group consisting of —CH₂OH, —CH₂OP(O)(OH)₂, and —CH₂OC(O)CH(R³⁷)NH₂; R^(2b) is —CH₃; and R³⁷ is —CH(CH₃)₂.
 10. The compound of claim 27, where R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—; R¹⁸ and R¹⁹ are independently selected from the group consisting of H and —C₁₋₆alkyl; and R^(2b) is —CH₃.
 11. The compound of claim 27, where Z is —CH—.
 12. The compound of claim 27, where Z is —N—.
 13. The compound of claim 27, where R³ is absent or is selected from the group consisting of H; halo; —C₀₋₅alkylene-OH; —NH₂; —C₁₋₆alkyl; —CF₃; —C₃₋₇cycloalkyl; —C₀₋₂alkylene-O—C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; —NHC(O)R²⁴; ═O; —NO₂; —C(CH₃)═N(OH); phenyl optionally substituted with one or two groups independently selected from the group consisting of halo, —OH, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl; naphthalenyl; pyridinyl; pyrazinyl; pyrazolyl optionally substituted with methyl; thiophenyl optionally substituted with methyl or halo; furanyl; and —CH₂-morpholinyl; and R²¹ is H.
 14. The compound of claim 27, where R³ is —C₀₋₁alkylene-COOR²¹; and R²¹ is selected from the group consisting of —C₁₋₆alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R²⁵, —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,


15. The compound of claim 27, where R³ is selected from the group consisting of H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²⁰ is —C₁₋₆alkyl; R²¹ is H; and R²² and R²³ are independently selected from the group consisting of —C₁₋₆alkyl, —(CH₂)₂OCH₃, and —C₃₋₇cycloalkyl; or R²² and R²³ are taken together to form a saturated —C₃₋₅heterocycle.
 16. The compound of claim 27, where R⁴ is absent or is selected from the group consisting of H; —OH; —C₁₋₆alkyl; —C₁₋₂alkylene-COOR³⁵; —CH₂OC(O)CH(R³⁶)NH₂; —CH₂CH(OH)CH₂OH; pyridinyl; and phenyl or benzyl optionally substituted with one or more groups selected from the group consisting of halo, —COOR³⁵, —OCH₃, —OCF₃, and —SCF₃; and R³⁵ is H.
 17. The compound of claim 27, where R⁴ is selected from the group consisting of —OCH₂OC(O)CH₃; —CH₂OP(O)(OH)₂; —C₁₋₂alkylene-COOR³⁵; and phenyl or benzyl substituted with at least one —COOR³⁵ group; where R³⁵ is selected from the group consisting of —C₁₋₆alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R²⁵, —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,


18. The compound of claim 27, where R⁴ is the group consisting of H, —OH, —C₁₋₆alkyl, —CH₂OC(O)CH(R³⁶)NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and benzyl.
 19. The compound of claim 27, where a is
 0. 20. The compound of claim 27, where b is 0 or b is 1 and R⁶ is halo.
 21. The compound of claim 27, where the methylene linker on the biphenyl is substituted with two —CH₃ groups.
 22. The compound of claim 27, where R¹ is —OR⁷; R⁷ is selected from the group consisting of H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from the group consisting of —C₁₋₆alkyl, —O—C₁₋₆alkyl, —O—C₃₋₇cycloalkyl, —CH[CH(CH₃)₂]—NH₂, and —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl; R¹² and R¹³ are —C₁₋₆alkyl or are taken together as —(CH₂)₃—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³¹ is selected from the group consisting of —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —CH₃; R^(2a) is —CH₂OH and R^(2b) is H; or R^(2a) is selected from the group consisting of —CH₂OH, —CH₂OP(O)(OH)₂, and —CH₂OC(O)CH(R³⁷)NH₂, R^(2b) is —CH₃, and R³⁷ is —CH(CH₃)₂; or R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹—, R¹⁸ and R¹⁹ are independently selected from the group consisting of H and —C₁₋₆alkyl, and R^(2b) is —CH₃; Z is —CH—; X is selected from the group consisting of pyrazole, imidazole, triazole, benzotriazole, oxazole, isoxazole, pyrimidine, pyridazine, benzimidazole, pyran, and pyridyltriazole; R³ is selected from the group consisting of H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²⁰ is —C₁₋₆alkyl; R²¹ is H; R²² and R²³ are independently selected from the group consisting of —C₁₋₆alkyl, —(CH₂)₂OCH₃, and —C₃₋₇cycloalkyl; or R²² and R²³ are taken together to form a saturated —C₃₋₅heterocycle; R⁴ is selected from the group consisting of H, —OH, —C₁₋₆alkyl, —CH₂OC(O)CH(R⁶)NH₂, —CH₂OP(O)(OH)₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and benzyl; a is 0; b is 0 or b is 1 and R⁶ is halo; and the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups.
 23. The compound of claim 27, where X is selected from the group consisting of pyrazole, triazole, benzotriazole, oxazole, isoxazole, and pyrimidine; R³ is selected from the group consisting of H; halo; —C₀₋₅alkylene-OH; —C₁₋₆alkyl; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; ═O; phenyl substituted with one halo; and pyridinyl; R²¹ is H; R²² and R²³ are taken together to form a saturated —C₃₋₅heterocycle; R⁴ is selected from the group consisting of H and —OH; a is 0; b is 0 or b is 1 and R⁶ is halo; and the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups. 24-26. (canceled)
 27. A compound selected from the group consisting of:

or a salt thereof; where R¹ is selected from the group consisting of —OR⁷ and —NR⁸R⁹; R^(1P) is selected from the group consisting of —O—P³, —NHP², and —NH(O—P⁴); R^(2a) is selected from the group consisting of —CH₂OH, —CH—OP(O)(OH)₂, and —CH₂OC(O)CH(R³⁷)NH₂; or R^(2a) is taken together with R⁷ to form —CH₂O—CR¹⁸R¹⁹— or is taken together with R⁸ to form —CH₂O—C(O)—; R^(2b) is selected from the group consisting of H and —CH₃, or is taken together with R^(2a) to form —CH₂—O—CH₂—; Z is selected from the group consisting of —CH— and —N—; X is a —C₁₋₉heteroaryl; R³ is absent or is selected from the group consisting of H; halo; —C₀₋₅alkylene-OH: —NH; —C₁₋₆alkyl; —CF₃; —C₃₋₇cycloalkyl: —C₀₋₂alkylene-O—C₁₋₆alkyl; —C(O)R²⁰; —C₀₋₁alkylene-COOR²¹; —C(O)NR²²R²³; —NHC(O)R²⁴; ═O; —NO₂; —C(CH₃)═N(OH); phenyl optionally substituted with one or two groups independently selected from the group consisting of halo, —OH, —CF₃, —OCH₃, —NHC(O)CH₃, and phenyl; naphthalenyl; pyridinyl; pyrazinyl; pyrazolyl optionally substituted with methyl; thiophenyl optionally substituted with methyl or halo; furanyl; and —CH₂-morpholinyl; and R³, when present, is attached to a carbon atom; R^(3P) is selected from the group consisting of —C₀₋₅alkylene-O—P⁴, —C₀₋₁alkylene-COO—P³, and phenyl substituted with —O—P⁴; R⁴ is absent or is selected from the group consisting of H; —OH; —C₁₋₆alkyl; —C₁₋₂alkylene-COOR³⁵; —CH₂OC(O)H(R³⁶)NH₂; —OCH₂OC(O)CH(R³⁶)NH₂; —OCH₂OC(O)CH₃; —CH₂OP(O)(OH)₂; —CH₂CH(OH)CH₂OH; —CH[CH(CH₃)₂]—NHC(O)—C₁₋₆alkyl; pyridinyl; and phenyl or benzyl optionally substituted with one or more groups selected from the group consisting of halo, —COOR³⁵, —OCH₃, —OCF₃, and —SCF₃; and R⁴, when present, is attached to a carbon or nitrogen atom; or R³ and R⁴ are taken together to form -phenylene-O—CH₁₋₃— or -phenylene-O—CH₂—CHOH—CH₂—; R^(4P) is selected from the group consisting of —O—P⁴; —C₁₋₂alkylene-COO—P³; and phenyl or benzyl substituted with —COO—P³; a is 0 or 1; R⁵ is selected from the group consisting of halo, —CH₃, —CF₃, and —CN; b is 0 or an integer from 1 to 3; each R⁶ is independently selected from the group consisting of halo, —OH, —CH₃, —OCH₃, and —CF₃; R⁷ is selected from the group consisting of H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹²R¹³, —C₁₋₆alkylene-C(O)R³¹, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from the group consisting of —C₁₋₆alkyl, —O—C₁₋₆allyl-C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹²R¹³, —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂OOCH₃; and R¹² and R¹³ are independently selected from the group consisting of H, —C₁₋₆alkyl, and benzyl, or R¹² and R¹³ are taken together as —(CH₂)₃—, —C(O)—(CH₂)₃—, or —(CH₂)O(CH₂)—; R³¹ is selected from the group consisting of —O—C₁₋₆alkyl, —O-benzyl, and —NR¹²R¹³; and R³² is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; R⁸ is selected from the group consisting of H, —OH, —OC(O)R¹⁴, —CH₂COOH, —O-benzyl, -pyridyl, and —OC(S)NR¹⁵R¹⁶; R¹⁴ is selected from the group consisting of H, —C₁₋₆alkyl, —C₆₋₁₀aryl, —OCH₂—C₆₋₁₀aryl, —CH₂O—C₆₋₁₀aryl, and —NR¹⁵R¹⁶; and R¹⁵ and R¹⁶ are independently selected from the group consisting of H and —C₁₋₄alkyl; R⁹ is selected from the group consisting of H, —C₁₋₆alkyl, and —C(O)—R¹⁷; and R¹⁷ is selected from the group consisting of H, —C₁₋₆alkyl, —C₃₋₇cycloalkyl, —C₆₋₁₀aryl, and —C₁₋₉heteroaryl; R¹⁸ and R¹⁹ are independently selected from the group consisting of H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or R¹⁸ and R¹⁹ are taken together to form ═O; R²⁰ is selected from the group consisting of H and —C₁₋₆alkyl; R²¹ and R³⁵ are independently selected from the group consisting of H, —C₁₋₆alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R²⁵, —C₁₋₆alkylene-NR²⁷R²⁸, —C₁₋₆alkylene-C(O)R³³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R²⁵ is selected from the group consisting of —C₁₋₆allyl-O—C₁₋₆allyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR²⁷R²⁸, —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)—C₁₋₆alkyl, and —CH(NH₂)CH₂OOCH₃; R²⁷ and R²⁸ are independently selected from the group consisting of H, —C₁₋₆alkyl, and benzyl; or R²⁷ and R²⁸ are taken together as —(CH₂)—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R³³ is selected from the group consisting of —O—C₁₋₆alkyl, —O-benzyl, and —NR²⁷R²⁸; and R³⁴ is —C₁₋₆alkyl or —C₀₋₆allylene-C₆₋₁₀aryl; R²² and R²³ are independently selected from the group consisting of H, —C₁₋₆alkyl, C₃₋₇cycloalkyl, and —(CH₂)₂-imidazolyl; or R²² and R²³ are taken together to form a saturated or partially unsaturated —C₃₋₅heterocycle optionally substituted with halo, —OH, —COOH, or —CONH₂; and optionally containing an oxygen atom in the ring; R²⁴ is selected from the group consisting of —C₁₋₆alkyl; —C₀₋₁alkylene-O—C₁₋₆alkyl; phenyl optionally substituted with halo or —OCH₃; and —C₁₋₉heteroaryl; R³⁶ is selected from the group consisting of H, —CH(CH₃)₂, phenyl, and benzyl; and R³⁷ is selected from the group consisting of H, —CH(CH₃)₂, phenyl, and benzyl; where each alkyl group in R¹, R³, and R⁴ is optionally substituted with 1 to 8 fluoro atoms; and; where the methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl; P² is an amino-protecting group selected from the group consisting of t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; P³ is a carboxy-protecting group selected from the group consisting of methyl, ethyl, t-butyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, trimethylsilyl, t-butyldimethylsilyl, and diphenylmethyl; and P⁴ is a hydroxyl-protecting group selected from the group consisting of —C₁₋₆alkyl, triC₁₋₆alkylsilyl, —C₁₋₆alkanoyl, benzoyl, benzyl, p-methoxybenzyl, 9-fluorenylmethyl, and diphenylmethyl. 28-31. (canceled) 